diff --git a/lib/bcoin/block.js b/lib/bcoin/block.js
index e7f870fa..6c38b230 100644
--- a/lib/bcoin/block.js
+++ b/lib/bcoin/block.js
@@ -48,3 +48,7 @@ Block.prototype.verify = function verify() {
 Block.prototype.render = function render(framer) {
   return [];
 };
+
+Block.prototype.hasMerkle = function hasMerkle(hash) {
+  return this.hashes.indexOf(hash) !== -1;
+};
diff --git a/lib/bcoin/chain.js b/lib/bcoin/chain.js
index 30a8db70..c9635a33 100644
--- a/lib/bcoin/chain.js
+++ b/lib/bcoin/chain.js
@@ -15,6 +15,11 @@ function Chain(options) {
   this.options = options || {};
   this.block = {
     list: [],
+
+    // Bloom filter for all merkle trees
+    merkleBloom: new bcoin.bloom(8 * 1024 * 1024, 16, 0xdeadbeed),
+
+    // Bloom filter for all known blocks
     bloom: new bcoin.bloom(8 * 1024 * 1024, 16, 0xdeadbeef)
   };
   this.orphan = {
@@ -95,15 +100,15 @@ Chain.prototype.add = function add(block) {
     var hash = block.hash('hex');
     var prev = block.prevBlock;
 
-    // If previous block wasn't ever seen - add current to orphans
+    // If the block is already known to be an orphan
     if (this.orphan.map[prev])
       break;
+
+    // If previous block wasn't ever seen - add current to orphans
     if (!this.probeIndex(hash, block.ts) && !this.probeIndex(prev, block.ts)) {
       this.orphan.count++;
       this.orphan.map[prev] = block;
 
-      // Add block to bloom filter, as we now have it in memory
-      this.block.bloom.add(hash, 'hex');
       this.emit('missing', prev, this.getRange(block.ts));
       break;
     }
@@ -124,6 +129,7 @@ Chain.prototype.add = function add(block) {
     // At least one block was added
     res = true;
     this.block.list.push(block);
+    this._bloomBlock(block);
 
     if (!this.orphan.map[hash])
       break;
@@ -148,21 +154,48 @@ Chain.prototype._compress = function compress() {
   // Bloom filter rebuilt is needed
   this.block.list = this.block.list.slice(-1000);
   this.block.bloom.reset();
+  this.block.merkleBloom.reset();
 
   for (var i = 0; i < this.block.list.length; i++)
-    this.block.bloom.add(this.block.list[i].hash());
+    this._bloomBlock(this.block.list[i]);
+};
+
+Chain.prototype._bloomBlock = function _bloomBlock(block) {
+  this.block.bloom.add(block.hash(), 'hex');
+  for (var i = 0; i < block.hashes.length; i++)
+    this.block.merkleBloom.add(block.hashes[i], 'hex');
 };
 
 Chain.prototype.has = function has(hash) {
   return this.probeIndex(hash) || !!this.orphan.map[hash];
 };
 
+Chain.prototype.hasMerkle = function hasMerkle(hash) {
+  if (!this.block.merkleBloom.test(hash, 'hex'))
+    return false;
+
+  hash = utils.toHex(hash);
+  for (var i = 0; i < this.block.list.length; i++)
+    if (this.block.list[i].hasMerkle(hash))
+      return true;
+
+  return false;
+};
+
 Chain.prototype.get = function get(hash, cb) {
   // Cached block found
   if (this.block.bloom.test(hash, 'hex')) {
-    for (var i = 0; i < this.block.list.length; i++)
-      if (this.block.list[i].hash('hex') === hash)
-        return cb(this.block.list[i]);
+    for (var i = 0; i < this.block.list.length; i++) {
+      if (this.block.list[i].hash('hex') === hash) {
+        // NOTE: we return right after the statement - so `i` should be valid
+        // at the time of nextTick call
+        var self = this;
+        process.nextTick(function() {
+          cb(self.block.list[i]);
+        });
+        return;
+      }
+    }
     assert(false);
   }
 
@@ -185,11 +218,14 @@ Chain.prototype.covers = function covers(ts) {
   return ts >= this.index.ts[0];
 };
 
-Chain.prototype.hashesFrom = function hashesFrom(ts, index) {
-  var pos = utils.binaryInsert(this.index.ts, ts - 2 * 3600, compareTs, true);
-  if (pos > 0)
-    pos--;
-  return this.index.hashes.slice(pos);
+Chain.prototype.hashesInRange = function hashesInRange(start, end) {
+  var ts = this.index.ts;
+
+  var pos = utils.binaryInsert(ts, start - 2 * 3600, compareTs, true);
+  start = Math.max(0, pos - 1);
+  var pos = utils.binaryInsert(ts, end + 2 * 3600, compareTs, true);
+  end = pos;
+  return this.index.hashes.slice(start, end);
 };
 
 Chain.prototype.getLast = function getLast() {
diff --git a/lib/bcoin/pool.js b/lib/bcoin/pool.js
index 38018abc..6ca0d6a3 100644
--- a/lib/bcoin/pool.js
+++ b/lib/bcoin/pool.js
@@ -1,4 +1,5 @@
 var assert = require('assert');
+var async = require('async');
 var util = require('util');
 var EventEmitter = require('events').EventEmitter;
 
@@ -25,6 +26,7 @@ function Pool(options) {
   this.maxRetries = options.maxRetries || 300;
   this.requestTimeout = options.requestTimeout || 10000;
   this.chain = new bcoin.chain();
+  this.watchList = [];
   this.bloom = new bcoin.bloom(8 * 10 * 1024,
                                10,
                                (Math.random() * 0xffffffff) | 0),
@@ -37,10 +39,26 @@ function Pool(options) {
     load: null
   };
   this.block = {
-    lastHash: null,
-    queue: [],
+    lastHash: null
+  };
+  this.request = {
+    map: {},
     active: 0,
-    requests: {}
+    queue: []
+  };
+  this.validate = {
+    // 5 days scan delta for obtaining TXs
+    delta: 5 * 24 * 3600,
+
+    // Minimum verification depth
+    minDepth: options.minValidateDepth || 1,
+
+    // getTx map
+    map: {},
+
+    // Validation cache
+    cache: [],
+    cacheSize: 1000
   };
 
   this.createConnection = options.createConnection;
@@ -58,10 +76,19 @@ Pool.prototype._init = function _init() {
 
   var self = this;
   this.chain.on('missing', function(hash, range) {
-    self._requestBlock(hash, true);
+    self._request('block', hash, { force: true });
     self._scheduleRequests();
     self._loadRange(range);
   });
+
+  setInterval(function() {
+    console.log('a %d q %d o %d r %d',
+                self.request.active, self.request.queue.length,
+                self.chain.orphan.count,
+                self.chain.request.count);
+    if (self.chain.request.count === 1)
+      console.log(Object.keys(self.chain.request.map));
+  }, 1000);
 };
 
 Pool.prototype._addLoader = function _addLoader() {
@@ -92,8 +119,7 @@ Pool.prototype._addLoader = function _addLoader() {
 
   function destroy() {
     // Chain is full and up-to-date
-    if (self.block.lastHash === null &&
-        self.chain.isFull()) {
+    if (self.block.lastHash === null && self.chain.isFull()) {
       clearTimeout(timer);
       peer.removeListener('close', onclose);
       self._removePeer(peer);
@@ -113,7 +139,7 @@ Pool.prototype._addLoader = function _addLoader() {
 
     // Request each block
     hashes.forEach(function(hash) {
-      self._requestBlock(hash);
+      self._request('block', hash);
     });
 
     self._scheduleRequests();
@@ -143,7 +169,7 @@ Pool.prototype._loadRange = function _loadRange(range) {
 };
 
 Pool.prototype._load = function _load() {
-  if (this.block.queue.length >= this.load.hwm) {
+  if (this.request.queue.length >= this.load.hwm) {
     this.load.hiReached = true;
     return false;
   }
@@ -196,27 +222,20 @@ Pool.prototype._addPeer = function _addPeer() {
   });
 
   peer.on('merkleblock', function(block) {
-    var has = self.chain.has(block);
     self.chain.add(block);
-    var req = self.block.requests[block.hash('hex')];
-    if (!req)
-      return;
-    assert(!has);
-    req.finish(block);
+    self._response(block);
   });
 
   peer.on('notfound', function(items) {
     items.forEach(function(item) {
-      if (item.type !== 'filtered')
-        return;
-
-      var req = self.block.requests[utils.toHex(item.hash)];
+      var req = self.request.map[utils.toHex(item.hash)];
       if (req)
         req.finish(null);
     });
   });
 
   peer.on('tx', function(tx) {
+    self._response(tx);
     self.emit('tx', tx);
   });
 };
@@ -235,31 +254,59 @@ Pool.prototype._removePeer = function _removePeer(peer) {
 };
 
 Pool.prototype.watch = function watch(id) {
-  if (typeof id === 'string')
-    id = utils.toArray(id, 'hex');
+  if (this.bloom.test(id, 'hex'))
+    return;
+
+  this.watchList.push(utils.toHex(id));
   if (id)
-    this.bloom.add(id);
+    this.bloom.add(id, 'hex');
+  if (this.peers.load)
+    this.peers.load.updateWatch();
   for (var i = 0; i < this.peers.block.length; i++)
     this.peers.block[i].updateWatch();
 };
 
-Pool.prototype.search = function search(id, limit, cb) {
+Pool.prototype.unwatch = function unwatch(id) {
+  if (!this.bloom.test(id, 'hex'))
+    return;
+
+  id = utils.toHex(id);
+  var index = this.watchList.indexOf(id);
+  if (index === -1)
+    return;
+  this.watchList.splice(index, 1);
+
+  // Reset bloom filter
+  this.bloom.reset();
+  for (var i = 0; i < this.watchList.length; i++)
+    this.bloom.add(this.watchList[i], 'hex');
+
+  // Resend it to peers
+  if (this.peers.load)
+    this.peers.load.updateWatch();
+  for (var i = 0; i < this.peers.block.length; i++)
+    this.peers.block[i].updateWatch();
+};
+
+Pool.prototype.search = function search(id, range) {
   if (typeof id === 'string')
     id = utils.toArray(id, 'hex');
 
-  // Optional limit argument
-  if (typeof limit === 'function') {
-    cb = limit;
-    limit = null;
-  }
+  if (range)
+    range = { start: range.start, end: range.end };
+  else
+    range = { start: 0, end: 0 };
 
   // Last 5 days by default, this covers 1000 blocks that we have in the
   // chain by default
-  if (!limit)
-    limit = (+new Date / 1000 - 432000);
+  if (!range.end)
+    range.end = +new Date / 1000;
+  if (!range.start)
+    range.start = +new Date / 1000 - 432000;
 
   var self = this;
-  var hashes = this.chain.hashesFrom(limit);
+  var e = new EventEmitter();
+  var hashes = this.chain.hashesInRange(range.start, range.end);
   var waiting = hashes.length;
 
   this.watch(id);
@@ -270,36 +317,63 @@ Pool.prototype.search = function search(id, limit, cb) {
       // Get block's prev and request it and all of it's parents up to
       // the next known block hash
       self.chain.get(block.prevBlock, function() {
-        if (--waiting === 0)
-          cb();
+        waiting--;
+        e.emit('progress', hashes.length - waiting, hashes.length);
+        if (waiting === 0) {
+          self.unwatch(id);
+          e.emit('end');
+        }
       });
     });
   }, this);
+
+  // Empty search
+  if (hashes.length === 0) {
+    process.nextTick(function() {
+      e.emit('end', true);
+    });
+  }
+
+  return e;
 };
 
-Pool.prototype._requestBlock = function _requestBlock(hash, force) {
+Pool.prototype._request = function _request(type, hash, options, cb) {
   if (typeof hash === 'string')
     hash = utils.toArray(hash, 'hex');
 
-  // Block should be not in chain, or be requested
-  if (!force && this.chain.has(hash))
-    return;
+  // Optional `force`
+  if (typeof options === 'function') {
+    cb = options;
+    options = {};
+  }
+  if (!options)
+    options = {};
 
   var hex = utils.toHex(hash);
-  if (this.block.requests[hex])
+  if (this.request.map[hex])
+    return this.request.map[hex].addCallback(cb);
+
+  // Block should be not in chain, or be requested
+  if (!options.force && type === 'block' && this.chain.has(hash))
     return;
 
-  var req = new BlockRequest(this, hex);
-  this.block.requests[hex] = req;
-  this.block.queue.push(req);
+  var req = new LoadRequest(this, type, hex, cb);
+  req.add(options.noQueue);
+};
+
+Pool.prototype._response = function _response(entity) {
+  var req = this.request.map[entity.hash('hex')];
+  if (!req)
+    return;
+  req.finish(entity);
 };
 
 Pool.prototype._scheduleRequests = function _scheduleRequests() {
-  if (this.block.active > this.parallel / 2)
+  if (this.request.active > this.parallel / 2)
     return;
 
   // No need to wait - already have enough data
-  if (this.block.queue.length > this.parallel) {
+  if (this.request.queue.length > this.parallel) {
     if (this.load.timer !== null)
       clearTimeout(this.load.timer);
     this.load.timer = null;
@@ -318,17 +392,18 @@ Pool.prototype._scheduleRequests = function _scheduleRequests() {
 };
 
 Pool.prototype._doRequests = function _doRequests() {
-  if (this.block.active >= this.parallel)
+  if (this.request.active >= this.parallel)
     return;
 
   // No peers so far
   if (this.peers.block.length === 0)
     return;
 
-  var above = this.block.queue.length >= this.load.lwm;
-  var items = this.block.queue.slice(0, this.parallel - this.block.active);
-  this.block.queue = this.block.queue.slice(items.length);
-  var below = this.block.queue.length < this.load.lwm;
+  var queue = this.request.queue;
+  var above = queue.length >= this.load.lwm;
+  var items = queue.slice(0, this.parallel - this.request.active);
+  this.request.queue = queue.slice(items.length);
+  var below = this.request.queue.length < this.load.lwm;
 
   // Watermark boundary crossed, load more blocks
   if (above && below && this.load.hiReached)
@@ -345,9 +420,155 @@ Pool.prototype._doRequests = function _doRequests() {
   }
 };
 
-function BlockRequest(pool, hash) {
+Pool.prototype.getTx = function getTx(hash, range, cb) {
+  hash = utils.toHex(hash);
+
+  if (typeof range === 'function') {
+    cb = range;
+    range = null;
+  }
+
+  // Do not perform duplicate searches
+  if (this.validate.map[hash])
+    return this.validate.map[hash].push(cb);
+
+  var cbs = [ cb ];
+  this.validate.map[hash] = cbs;
+  // Add request without queueing it to get notification at the time of load
+  var tx = null;
+  var finished = false;
+  var req = this._request('tx', hash, { noQueue: true }, function(t) {
+    finished = true;
+    tx = t;
+  });
+
+  // Do incremental search until the TX is found
+  var delta = this.validate.delta;
+
+  // Start from the existing range if given
+  if (range)
+    range = { start: range.start, end: range.end };
+  else
+    range = { start: (+new Date / 1000) - delta, end: 0 };
+
+  var self = this;
+  doSearch();
+
+  function doSearch() {
+    console.log('Searching for ' + hash, range);
+    var e = self.search(hash, range);
+    e.on('end', function(empty) {
+      if (finished) {
+        delete self.validate.map[hash];
+        cbs.forEach(function(cb) {
+          cb(tx, range);
+        });
+        return;
+      }
+
+      // Tried everything, but still no matches
+      if (empty)
+        return cb(null);
+
+      // Not found yet, continue scanning
+      range.end = range.start;
+      range.start -= delta;
+      if (range.start < 0)
+        range.start = 0;
+
+      doSearch();
+    });
+  }
+};
+
+Pool.prototype._addValidateCache = function addValidateCache(tx, result) {
+  this.validate.cache.push({
+    hash: tx.hash('hex'),
+    result: result
+  });
+  if (this.validate.cache.length > this.validate.cacheSize)
+    this.validate.cache = this.validate.cache.slice(-this.validate.cacheSize);
+};
+
+Pool.prototype._probeValidateCache = function probeValidateCache(tx) {
+  for (var i = 0; i < this.validate.cache.length; i++) {
+    var entry = this.validate.cache[i];
+    if (entry.hash === tx.hash('hex'))
+      return entry.result;
+  }
+};
+
+Pool.prototype.validateTx = function validateTx(tx, cb, _params) {
+  // Probe cache first
+  var result = this._probeValidateCache(tx);
+  if (result) {
+    process.nextTick(function() {
+      cb(null, result);
+    });
+    return;
+  }
+
+  if (!_params)
+    _params = { depth: 0, range: null };
+
+  // Propagate range to improve speed of search
+  var depth = _params.depth;
+  var range = _params.range;
+
+  var result = {
+    included: this.chain.hasMerkle(tx.hash()),
+    valid: false
+  };
+
+  console.log('validateTx: ', tx.hash('hex'), depth);
+  if (depth > this.validate.minDepth && result.included) {
+    result.valid = true;
+    process.nextTick(function() {
+      cb(null, result);
+    });
+    return;
+  }
+
+  // Load all inputs and validate them
+  var self = this;
+  async.map(tx.inputs, function(input, cb) {
+    var out = null;
+    console.log('load input: ', input.out.hash);
+    self.getTx(input.out.hash, range, function(t, range) {
+      console.log('got input for: ', tx.hash('hex'), !!t);
+      out = t;
+      self.validateTx(out, onSubvalidate, {
+        depth: depth + 1,
+        range: range
+      });
+    });
+
+    function onSubvalidate(err, subres) {
+      if (err)
+        return cb(err);
+
+      cb(null, {
+        input: input,
+        tx: out,
+        valid: subres.valid
+      });
+    }
+  }, function(err, inputs) {
+    if (err) {
+      result.valid = false;
+      return cb(err, result);
+    }
+
+    self._addValidateCache(tx, result);
+    console.log(inputs);
+  });
+};
+
+function LoadRequest(pool, type, hash, cb) {
   this.pool = pool
+  this.type = type;
   this.hash = hash;
+  this.cbs = cb ? [ cb ] : [];
   this.timer = null;
   this.peer = null;
   this.ts = +new Date;
@@ -359,12 +580,12 @@ function BlockRequest(pool, hash) {
   };
 }
 
-BlockRequest.prototype.start = function start(peer) {
+LoadRequest.prototype.start = function start(peer) {
   var self = this;
   assert(!this.active);
 
   this.active = true;
-  this.pool.block.active++;
+  this.pool.request.active++;
 
   assert(!this.timer);
   this.timer = setTimeout(function() {
@@ -376,19 +597,31 @@ BlockRequest.prototype.start = function start(peer) {
   this.peer = peer;
   this.peer.once('close', this.onclose);
 
+  var reqType;
+  if (this.type === 'block')
+    reqType = 'filtered';
+  else if (this.type === 'tx')
+    reqType = 'tx';
+
   return {
-    type: 'filtered',
+    type: reqType,
     hash: this.hash
   };
 };
 
-BlockRequest.compare = function compare(a, b) {
+LoadRequest.compare = function compare(a, b) {
   return a.ts - b.ts;
 };
 
-BlockRequest.prototype.clear = function clear() {
+LoadRequest.prototype.add = function add(noQueue) {
+  this.pool.request.map[this.hash] = this;
+  if (!noQueue)
+    this.pool.request.queue.push(this);
+};
+
+LoadRequest.prototype.clear = function clear() {
   assert(this.active);
-  this.pool.block.active--;
+  this.pool.request.active--;
   this.active = false;
   this.peer.removeListener('close', this.onclose);
   this.peer = null;
@@ -396,9 +629,9 @@ BlockRequest.prototype.clear = function clear() {
   this.timer = null;
 };
 
-BlockRequest.prototype.retry = function retry() {
+LoadRequest.prototype.retry = function retry() {
   // Put block into the queue, ensure that the queue is always sorted by ts
-  utils.binaryInsert(this.pool.block.queue, this, BlockRequest.compare);
+  utils.binaryInsert(this.pool.request.queue, this, LoadRequest.compare);
   var peer = this.peer;
   this.clear();
 
@@ -410,21 +643,29 @@ BlockRequest.prototype.retry = function retry() {
   this.pool._scheduleRequests();
 };
 
-BlockRequest.prototype.finish = function finish() {
+LoadRequest.prototype.finish = function finish(entity) {
   if (this.active) {
     this.clear();
   } else {
     // It could be that request was never sent to the node, remove it from
     // queue and forget about it
-    var index = this.pool.block.queue.indexOf(this);
+    var index = this.pool.request.queue.indexOf(this);
     if (index !== -1)
-      this.pool.block.queue.splice(index, 1);
+      this.pool.request.queue.splice(index, 1);
     assert(!this.peer);
     assert(!this.timer);
   }
-  delete this.pool.block.requests[this.hash];
+  delete this.pool.request.map[this.hash];
 
   // We may have some free slots in queue now
   this.pool._scheduleRequests();
-  this.pool.finished++;
+
+  this.cbs.forEach(function(cb) {
+    cb(entity);
+  });
+};
+
+LoadRequest.prototype.addCallback = function addCallback(cb) {
+  if (cb)
+    this.cbs.push(cb);
 };
diff --git a/lib/bcoin/tx.js b/lib/bcoin/tx.js
index 4e20c148..86a79e1e 100644
--- a/lib/bcoin/tx.js
+++ b/lib/bcoin/tx.js
@@ -23,6 +23,7 @@ function TX(data) {
       script: bcoin.script.parse(output.script)
     };
   });
+  this.lock = data.lock;
 
   this._hash = null;
   this._raw = data._raw || null;
@@ -43,3 +44,6 @@ TX.prototype.hash = function hash(enc) {
 TX.prototype.render = function render(framer) {
   return [];
 };
+
+TX.prototype.verify = function verify() {
+};
diff --git a/lib/bcoin/utils.js b/lib/bcoin/utils.js
index 148a82cd..25db902f 100644
--- a/lib/bcoin/utils.js
+++ b/lib/bcoin/utils.js
@@ -192,6 +192,9 @@ function zero2(word) {
 }
 
 function toHex(msg) {
+  if (typeof msg === 'string')
+    return msg;
+
   var res = '';
   for (var i = 0; i < msg.length; i++)
     res += zero2(msg[i].toString(16));
diff --git a/package.json b/package.json
index d0928215..5bc27f04 100644
--- a/package.json
+++ b/package.json
@@ -21,6 +21,7 @@
   },
   "homepage": "https://github.com/indutny/bcoin",
   "dependencies": {
+    "async": "^0.8.0",
     "bn.js": "^0.2.0",
     "elliptic": "^0.7.0",
     "hash.js": "^0.2.0"