Tommy Marcone was the childhood friend of Zach Lindsey, the star swimmer who vanished below the surface as "The Dead Pool" kicked off. Tommy was also Zach's go-to guy when he found that he needed to supplement his partial scholarship, and didn't feel that a normal job would fit, or pay, the bill. Tommy and Zach began stealing cars, a highly lucrative sideline, and a logical possible cause for murder, which was why Beckett and Castle eyed him as a suspect. However, time would show that Tommy was a loyal, if impetuous, friend, and the killing was the handiwork of another.