On the campus of Brill College, a foolish student, Philo, suspects Professor Tisdelle is about to commit a murder. Philo informs the editor of the student newspaper, Larry Campbell, whose girl friend, Betty is the professor's daughter, and the two young men arrive at the professor's classroom in time to see him demonstrate the laws of gravity, using two pistols. Later, following the prom, a bookish student, Craig Banning, and his landlady, find proctor Jeffrey Thompson dead in his apartment. Inspector Nat Corrigan suspects Professor Tisdelle when he finds Tisdelle's bonds among the dead man's belongings, and then Philo mentions the professor's guns. The inspector then finds one of the professor's guns in Larry's locker, but the professor's fingerprints have been faked. Professor Tisdelle pulls a gun on Craig and demands that he confess, but Craig jumps into the river and his body is not recovered. At the commencement exercises, under the assumption that Craig has died, the school agrees to give his diploma to his brother, who is actually Craig in disguise. As Craig goes up to accept his diploma, he is recognized, and he runs for an open window, climbing out and down a drainpipe. Craig loses his grip and falls however. Before he dies, Craig confesses that he killed Thompson when Thompson refused to give him any more exam answers.