At an ivy-covered boarding school a resourceful girl and her two close friends return for a new term and face cliques, petty rivalries, and a chain of perplexities that begin with a trivial quarrel and expand into missing items, anonymous letters, sabotage, and a dangerous accident. Accusations mount and evidence piles up while loyalties are tested; the girls investigate, conduct small experiments, and seek witnesses until a recalled detail breaks the case, leading to a dramatic confrontation and a resolution that clears the innocent and restores order among the students.