diff --git a/package.json b/package.json
index c530ebc9..0253c574 100644
--- a/package.json
+++ b/package.json
@@ -19,6 +19,7 @@
   "homepage": "https://github.com/vulcanize/erc20-watcher#readme",
   "dependencies": {
     "@types/lodash": "^4.14.168",
+    "apollo-type-bigint": "^0.1.3",
     "express": "^4.17.1",
     "express-graphql": "^0.12.0",
     "graphql": "^15.5.0",
diff --git a/src/erc20.graphql b/src/erc20.graphql
index e76e2896..690647b0 100644
--- a/src/erc20.graphql
+++ b/src/erc20.graphql
@@ -1,29 +1,100 @@
-type Author {
-  id: Int!
-  firstName: String
-  lastName: String
-  """
-  the list of Posts by this author
-  """
-  posts: [Post]
+#
+# ERC20 GQL schema
+#
+
+# Types
+
+# Support uint256 values.
+scalar BigInt
+
+# Proof for returned data. Serialized blob for now.
+# Will be converted into a well defined structure later.
+type Proof {
+  data: String!
 }
 
-type Post {
-  id: Int!
-  title: String
-  author: Author
-  votes: Int
+# Result type, with proof, for uint256 method return values.
+type ResultUInt256 {
+  value: BigInt!
+
+  # Proof from state/storage trie.
+  proof: Proof
 }
 
-# the schema allows the following query:
+# ERC20 Token https://eips.ethereum.org/EIPS/eip-20
+# ABI: https://ethereumdev.io/abi-for-erc20-contract-on-ethereum/
+type Token {
+  name: String!
+  symbol: String!
+  decimals: Int!
+  totalSupply: BigInt!
+}
+
+# Transfer Event
+# Emitted by: `function transfer(address _to, uint256 _value) public returns (bool success)`
+# Emitted by: `function transferFrom(address _from, address _to, uint256 _value) public returns (bool success)`
+type TransferEvent {
+  from: String!
+  to: String!
+  value: BigInt!
+}
+
+# Approval Event
+# Emittted by: `function approve(address _spender, uint256 _value) public returns (bool success)`
+type ApprovalEvent {
+  owner: String!
+  spender: String!
+  value: BigInt!
+}
+
+# All possible event types fired by an ERC20 contract.
+union TokenEvent = TransferEvent | ApprovalEvent
+
+# Result type, with proof, for event return values.
+type ResultEvent {
+  event: TokenEvent!
+
+  # Proof from receipts trie.
+  proof: Proof
+}
+
+
+#
+# Queries
+#
+
 type Query {
-  posts: [Post]
-  author(id: Int!): Author
+
+  # `function balanceOf(address _owner) public view returns (uint256 balance)`
+  balanceOf(
+    blockHash: String!
+    token: String!
+
+    owner: String!
+  ): ResultUInt256!
+
+  # `function allowance(address _owner, address _spender) public view returns (uint256 remaining)`
+  allowance(
+    blockHash: String!
+    token: String!
+
+    owner: String!
+    spender: String!
+  ): ResultUInt256!
+
+  # Get token events at a certain block, optionally filter by event name.
+  events(
+    blockHash: String!
+    token: String!
+    name: String
+  ): [ResultEvent!]
 }
 
-# this schema allows the following mutation:
-type Mutation {
-  upvotePost (
-    postId: Int!
-  ): Post
+#
+# Subscriptions
+#
+type Subscription {
+
+  # Watch for token events (at head of chain).
+  onTokenEvent(token: String!): ResultEvent!
 }
diff --git a/src/gql.ts b/src/gql.ts
index ee02d482..2884d1dc 100644
--- a/src/gql.ts
+++ b/src/gql.ts
@@ -1,36 +1,51 @@
+import 'lodash';
 import 'graphql-import-node';
-import { find, filter } from 'lodash';
 import { makeExecutableSchema } from '@graphql-tools/schema';
+import BigInt from 'apollo-type-bigint';
 
 import * as typeDefs from './erc20.graphql';
-import data from './mock-data';
-
-const { posts, authors } = data;
+import { blocks } from './mock-data';
 
 const resolvers = {
-  Query: {
-    posts: () => posts,
-    author: (_, { id }) => find(authors, { id }),
-  },
+  BigInt: new BigInt('bigInt'),
 
-  Mutation: {
-    upvotePost: (_, { postId }) => {
-      const post = find(posts, { id: postId });
-      if (!post) {
-        throw new Error(`Couldn't find post with id ${postId}`);
+  TokenEvent: {
+    __resolveType: (obj) => {
+      if (obj.owner) {
+        return 'ApprovalEvent';
+      }
+
+      return 'TransferEvent';
+    }
+  },
+
+  Query: {
+
+    balanceOf: (_, { blockHash, token, owner }) => {
+      console.log('balanceOf', blockHash, token, owner);
+
+      return {
+        value: blocks[blockHash][token].balanceOf[owner],
+        proof: { data: '' }
       }
-      post.votes += 1;
-      return post;
     },
-  },
 
-  Author: {
-    posts: author => filter(posts, { authorId: author.id }),
-  },
+    allowance: (_, { blockHash, token, owner, spender }) => {
+      console.log('allowance', blockHash, token, owner, spender);
 
-  Post: {
-    author: post => find(authors, { id: post.authorId }),
-  },
+      return {
+        value: blocks[blockHash][token].allowance[owner][spender],
+        proof: { data: '' }
+      }
+    },
+
+    events: (_, { blockHash, token, name }) => {
+      console.log('events', blockHash, token, name);
+      return blocks[blockHash][token].events
+        .filter(e => !name || name === e.name)
+        .map(e => ({ 'event': e }));
+    }
+  }
 };
 
 export const schema = makeExecutableSchema({
diff --git a/src/mock-data.ts b/src/mock-data.ts
index 994d9e10..08327859 100644
--- a/src/mock-data.ts
+++ b/src/mock-data.ts
@@ -1,17 +1,43 @@
-const authors = [
-  { id: 1, firstName: 'Tom', lastName: 'Coleman' },
-  { id: 2, firstName: 'Sashko', lastName: 'Stubailo' },
-  { id: 3, firstName: 'Mikhail', lastName: 'Novikov' },
-];
+// TODO: Pull mock data for 5 tokens from rinkeby.
 
-const posts = [
-  { id: 1, authorId: 1, title: 'Introduction to GraphQL', votes: 2 },
-  { id: 2, authorId: 2, title: 'Welcome to Meteor', votes: 3 },
-  { id: 3, authorId: 2, title: 'Advanced GraphQL', votes: 1 },
-  { id: 4, authorId: 3, title: 'Launchpad is Cool', votes: 7 },
-];
-
-export default {
-  posts,
-  authors
+export const tokens = {
+  '0xd87fea54f506972e3267239ec8e159548892074a': {
+    name: 'ChainLink Token',
+    symbol: 'LINK',
+    decimals: 18,
+    totalSupply: '1000000'
+  }
+};
+
+export const blocks = {
+  // Block hash.
+  '0x77b5479a5856dd8ec63df6aabf9ce0913071a6dda3a3d54f3c9c940574bcb8ab': {
+
+    // ERC20 token address.
+    '0xd87fea54f506972e3267239ec8e159548892074a': {
+      balanceOf: {
+        '0xDC7d7A8920C8Eecc098da5B7522a5F31509b5Bfc': 10000,
+        '0xCA6D29232D1435D8198E3E5302495417dD073d61': 500
+      },
+      allowance: {
+        '0xDC7d7A8920C8Eecc098da5B7522a5F31509b5Bfc': {
+          '0xCA6D29232D1435D8198E3E5302495417dD073d61': 100
+        }
+      },
+      events: [
+        {
+          name: 'Transfer',
+          from: '0xDC7d7A8920C8Eecc098da5B7522a5F31509b5Bfc',
+          to: '0xCA6D29232D1435D8198E3E5302495417dD073d61',
+          value: 500
+        },
+        {
+          name: 'Approval',
+          owner: '0xDC7d7A8920C8Eecc098da5B7522a5F31509b5Bfc',
+          spender: '0xCA6D29232D1435D8198E3E5302495417dD073d61',
+          value: 100
+        }
+      ]
+    }
+  }
 };
diff --git a/yarn.lock b/yarn.lock
index 6f3fb5b7..ff7363a3 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -943,6 +943,11 @@ anymatch@~3.1.1:
     normalize-path "^3.0.0"
     picomatch "^2.0.4"
 
+apollo-type-bigint@^0.1.3:
+  version "0.1.3"
+  resolved "https://registry.yarnpkg.com/apollo-type-bigint/-/apollo-type-bigint-0.1.3.tgz#9242115ca909b9467ba5c4bc6493a56a06984c0b"
+  integrity sha512-nyfwEWRZ+kon3Nnot20DufGm2EHZrkJoryYzw3soD+USdxhkcW434w1c/n+mjMLQDl86Z6EvlkvMX5Lordf2Wg==
+
 apollo-upload-client@14.1.3:
   version "14.1.3"
   resolved "https://registry.yarnpkg.com/apollo-upload-client/-/apollo-upload-client-14.1.3.tgz#91f39011897bd08e99c0de0164e77ad2f3402247"