CSI: NY - Season 1 Episode 2 Creatures of the Night

Junkie Jordy Thompkins was shot dead in an alleyway, but the bullet that killed him is missing. Taylor and Hawkes soon realise that a rat may have eaten the bullet, and finding the rat leads them to a robbery that occurred earlier that day. After Robin Prescott is found raped and beaten in Central Park with only a peony leaf on her clothing, Stella and Flack have the daunting task of trying to find the man who raped her, but Prescott has no memory of the crime.