When an unconscious man is lying on the street, another man stamps on his head, killing him. There's no CCTV, and the witnesses don't know him. But can a footwear specialist looking at the bruising on the body help identify the shoes worn by the killer? And, if so, will it be enough to identify him? And when Ministry of Sound's website is hacked, officers find out who's responsible, using an old computer gaming account.