The Double McGuffin

A group of boarding school students discover, in succession, a suitcase full of money, a dead body, and a dismembered hand. They are unable to convince the local police to take them seriously, because they have not secured any evidence and because the police chief (played by Kennedy) is suspicious of them due to their past misbehavior. They follow the evidence themselves and realize that a political assassination is planned at a school event. They foil the plot themselves.