On July 11, 1899 at 10 a.m., the Union Pacific Express has left Folsom, New Mexico, with 47 passengers on board. A few minutes later, gunfire and hurrying footsteps on the roof can be heard. Heavily armed bandits are here to rob honest citizens of their wallets and jewels. Will they succeed in taking the suitcase holding the Nice Valley Coal Company's weekly pay, despite it having been placed under the care of Marshal Samuel Ford? Will these bandits harm one another more than the Marshal since only the richest one of them can come out on top?

In Colt Express, you play a bandit robbing the train at the same time as other bandits, and your objective is to become the richest outlaw of the Old West. The game has five rounds, and each round has two phases:

Phase 1: Schemin' Each player plays 2-5 action cards, face up or face down depending on the type of the round. Instead of playing a card, a player may draw three cards from their deck.

Phase 2: Stealin' The action cards are played out in the order they were played, but a player's best laid plans might not pan out the way they hoped, due to mistakes and oversights!

The game takes place on a 3D train where the bandits can move from one car to another, run on the roof, punch or shoot other bandits, rob passengers, or draw the Marshal out of position. The train has as many cars as the number of players, and each car is seeded with gems, bags of loot or suitcases at the beginning of play.

Each player begins a round with six cards in hand, with each card showing one of these actions. At the beginning of a round, a round card is revealed, showing how many cards will be played; whether they'll be played face up or face down, individually or in pairs; and what action will occur at the end of the round (e.g., all bandits on the train move to the engine). You can grab up loot, gems or suitcases only by playing a "steal" card when in a train car that holds one of these items — but since everyone wants get these goods, you'll need to move, punch and shoot to get others out of the way. You can punch someone only in the same car as you, and when you do, the other bandit drops one of the goods he's gathered and is knocked into an adjacent car.

Each player's character has a unique power, such as starting the round with an extra card, playing your first card face down, or pocketing a bag of loot when you punch someone instead of letting it hit the ground.

You can shoot in an adjacent car or (if you're running on top of the train) anyone in sight, and when you do, you give that player one of your six bullet cards; the card being shuffled into the opponent's deck, possibly giving them a dead card in hand on a future turn and forcing them to draw instead of playing. If the Marshal ends up in the same car as you, he will be happy to give you a bullet, too.

At the end of the game, whoever fired the most bullets gets a $1,000 braggart bonus, and whoever bagged the richest haul wins!