A few spots of the victim's blood on a blue shirt convict a murderer when police deduce it was likely to be worn on the day of the killing. Detectives are left baffled by an apparently motiveless killing as they try to make sense of items left at the crime scene, but when they finally arrest a suspect, his vanity proves his undoing. Elsewhere, a rapper tells tales on himself when rap videos he posts online about his drug-dealing exploits mean the police come knocking at his door.

A USB stick containing key information about the production and supply of illegal drugs is found in a raid of a respectable businesswoman's house. Authorities tell police that packages being posted labelled as so-called ‘legal highs' are a front for dealing narcotics online, so detectives set about finding the factory manufacturing them, before setting their sights higher. Elsewhere, after seeing an increase in guns designed to fire blanks converted into deadly weapons, police target the man responsible.