An accident occurred inside Rikers prison. An inmate was stabbed dead and another one (Otto Sanchez) was wounded in what looked like a fight ended up badly. Right away the injured prisoner was bailed out and detectives start following him: they find him inside a pizza parlor, where they're shocked in realizing he's actually an undercover officer. So investigation comes back to square one. The CCTV footage inside the joint doesn't show what really happened because the murder occurred in a blind spot: the killing was staged very carefully. Due to prints found in the murder weapon (a shank) police manages to recognize the perp, a lowlife with two murders on his record but without any motives. Someone (a correction officer) set up everything as a payback for a previous rape made by the victim.
Correction officers stay very close to the defendant, trying to cover him up as a sort of fraternity. Anyway there are too little evidence and only a not so reliable witness, maybe the sender could get away with it at trial. Or maybe not? It depends on McCoy.