A nameless, ruthless man (Preston Foster) who identifies himself as Mr. Big is timing to the minute the arrival of two trucks. One is an armored car routinely picking up bags containing lots of money from a bank. The other truck delivers to a flower shop next door. The man's timing shows that, for a very few minutes, the schedule of both trucks coincidentally parks them next to each other. He is casing the armored car. He needs a gang to help him rob it. He selects three men for the gang—the addictive gambler Peter Harris (Jack Elam) wanted for murder, gum-chewing thug Boyd Kane (Neville Brand) and the womaniziing Tony Romano (Lee Van Cleef). When interviewing them, he wears a mask so they cannot identify him. He has selected them because each has a reason for fleeing the US. They will fit perfectly into Mr. Big's complex plan, which appears to be an ordinary robbery but is much more.