Instinct - Season 2 Episode 11

Two passerby discover a severed head in a pond near a park. Dylan and Lizzie investigate and find there are three additional severed heads in the pond, but no sign of the bodies. The coroner finds that the heads were all put in the pond at different times, and further finds that all four of the heads have s specific chemical in them. Julian is asked to help with some computer investigation once the identity of the most recent head is known, This leads to a strange medical experiment and a possible mad scientist. Meanwhile, Dylan has a visit from someone from his past.