There has been another Murder in Successville. A priceless piece of art has been stolen from right under DI Sleet's nose, and Bjork is murdered in the process. Sleet and his new sidekick Richard Osman wade into art's black market underworld to catch their culprit. Find the art, and they'll find the killer. This time they investigate Arsene Wenger, an avant-garde art collector whose new gallery is opening at a suspiciously convenient time. Sleet and Osman go undercover as turtle-necked arty types to get some answers. Hilary Clinton is an art teacher and a forger who claims to have gone straight. Richard Osman goes undercover as a student to glean some answers. Zayn Malik is a cat burglar who is a little down and out after being thrown out of his gang. Sleet and Osman break into a creepy paint factory to give Zayn an old-fashioned roughing-up, though Zayn turns the tables when he reveals some shocking truths about Sleet's dad. After coming to terms with his daddy issues, Sleet takes Richard Osman down to Successville's sewers to infiltrate a black market art auction ran by Bill Nighy. Have you kept your eyes and ears open for clues? Could you take out the right person?

This week we're thrown back in time to Victorian Successville, where guest rookie Martin Kemp is tasked with solving the very first Murder in Successville. Local lady of the night Rita Ora has been found slayed in an alley, and DI Sleet and Kemp are tasked with retracing her last steps around the cobbled streets of Successville. They investigate Will-i-am, a science professor who has always got the better of Sleet. Martin Kemp's investigation is disrupted, however, when Will-i-am tricks Sleet into drinking truth serum. Paloma Faith is the landlady of the local brothel where victim Rita worked. Martin Kemp and Sleet go undercover as criminal brothers - the Neville brothers - but there is some confusion as to who is supposed to be the cooler brother. Jonathon Ross is an upper-class gentleman who had no idea that his girlfriend Rita was working at a brothel. Sleet and Kemp go undercover to a gentleman's club where they manage to get invited to dine with Jonathon Ross and his good friend Jamie Oliver. With all three suspects facing execution by the firing squad, Sleet and Martin Kemp have to pick who they think the real murderer is. Have you kept your eyes and ears open for clues? Could you take out the right person?

Things get very strange in Successville as reporter Harry Hill is found dead, covered with radiation burns and surrounded with weird footprints that look like they belong to a monster... DI Sleet and his new celebrity sidekick Lorraine Kelly delve into all things supernatural as they grill this week's suspects: Ant and Dec, a couple of backwards hillbillies, who run mystery tours. With Sleet getting distracted by Dec's hip new line of craft beers, it's up to Lorraine to lead the investigation. Madonna is a recluse, having undergone shady medical tests many years ago at a shadowy chemical factory. Rumours of monsters and mutated creatures surround the factory, so Sleet and Lorraine try to get some intel from Madonna by posing as old high school friends. Someone clearly thinks Sleet and Lorraine are sticking their noses where they're not wanted, as they are captured by the owner of the mysterious factory, which turns out to be David Walliams.

DI Sleet and his sidekick Reggie Yates are going undercover on a stag do, spending 24 hours in Successville's top hotel. There is a murder to solve, but try telling that to an excitable murder detective who has found out there is a karaoke bar. When undercover detective Noel Edmonds is found dead in a bedroom in what looks like a sex game gone wrong, it is up to Reggie to lead the investigation. The pair must infiltrate an assassins' convention at the hotel, being held by the manager Michael McIntrye. Along the way, they investigate: Sharon Osbourne, the hotel's resident crooner, who recently spent a saucy night with the late Noel Edmonds. Venus and Serena Williams, two sister assassins with a deadly sibling rivalry. Adrian Chiles, the world's most deadly assassin. Will the duo get to the assassins' convention in time to take out whoever Reggie thinks murdered Noel Edmonds?

New police recruit Professor Green enters Successville amidst an epic rivalry between the supervillain known as the Termite and the town's masked vigilante superhero the Rattman. The Termite has struck again, killing the new police commissioner Bear Grylls, and it is up to DI Sleet and Pro Green to catch and unmask the Termite. The duo investigate Piers Morgan, Beyonce and a third suspect who is a bit of a surprise and a little too close to home. Plus there is an ending fit for any superhero when the Termite's true identity is revealed in an abandoned biscuit factory.

The previous episode ended in an epic cliffhanger as DI Sleet's superhero alter ego, The Rattman, was left in a life-or-death scenario at the hands of supervillain The Termite. In this retrospective of Murder In Successville's best bits, Sleet is having some self-reflection as he faces his toughest decision to date. He must turn his back on one of his personas forever, but will it be Sleet the cop or Sleet the superhero?