A 19-year-old college student is found dead on the tracks of the subway after apparently riding on top on the train. A shark's tooth is found embedded into his hand and four tropical fish are discovered in his stomach. The evidence points to murder, not an accident.

Meanwhile, Stella probes the murder of a commodities trader found dangling by a cord out of his office's 40th-floor window. The investigation reveals that the man was killed before he was tossed outside.