A gang of career criminals plots the robbery of an armored car company's headquarters. Although the robbery itself goes off as planned, it's not long before the gang members are fighting among themselves over everybody's share of the loot and trying to avoid capture by the police, who are pouring all their resources into capturing the robbers. Based on a real-life 1950 Brinks Armored Car Co. robbery in Boston.

Roger Quain, escorting two zoo-bound black panthers on the train from Milan to Paris, is unaware that a Western agent, Catherine Ullven, has hidden a microfilm in the collar of one of the animals. But when the train is derailed in the Swiss Alps and the panthers escape, she is forced to involve him in her mission, which now includes enemy agents hunting the microfilm, the animals, Catherine and Roger.