What is “murderabilia”? We meet Paul, a collector from Rochester, New York, whose serial killer collectables include Charles Manson’s guitars and an Arthur Shawcross car.

We also speak to Eric Holler, a murderabilia dealer who runs the website “Serial Killers Ink” and whose arch nemesis is a victims’ rights advocate.

We meet dealer Eric's harshest critic. Andy Kahan is a victims' rights advocate based in Houston, Texas, who passionately campaigns to outlaw the murderabilia trade in the US. We also order our own piece of murderabilia.

We take a trip to a true crime museum in Hastings, UK, and examine how our attitudes to murderabilia can change once it's safely behind glass.

We travel to Scotland and have tea and cake with a big-time collector. We continue to grapple with the idea that the way a piece of murderabilia is displayed can change our responses to it.

Our own piece of murderabilia arrives. What will it reveal? We also speak to criminologist and sociologist Dr Jack Denham, who helps tie up some loose ends in our thinking.

Body parts galore as we dive into the history of the celebrity criminal, with Dr Ruth Penfold-Mounce and actor Michael Badalucco, who played killer David Berkowitz in Spike Lee's film Summer of Sam.