Detective Murdoch investigates the death of Katie Buchanan who is found dead at the beach, on a hot summer’s day, by her friend Elaine Lawson. Both were entrants in a beauty pageant known as the Miss Purity competition, to select the new face of Alexander soap. Dr. Ogden, who is spending her day off at the beach finds what appears to be a large animal bite on the woman’s torso. Katie’s boyfriend, James Bennett, had recently left her for another competitor, Marie Nicholson and becomes the prime suspect. Inspector Brackenreid however is certain he saw a monster in Lake Ontario and Murdoch is skeptical until he too sees a creature in the water. Constable Crabtree is dismissive of any suggestion that there might be a monster in the water and pursues a more realistic line of inquiry.