 The body of unscrupulous stockbroker Gerald Parker suddenly appears in the penguin tank at the aquarium. Naturally, suspicion falls on his wife and her boyfriend, who were present. Inspector Piper investigates with the unsolicited aid of teacher Hildegard Withers, a witness who s taken an interest in the case; Piper develops a grudging respect for Miss Withers  acumen (and sharp tongue), as they search among the red herrings for the aquarium killer...