Series 1

When a body is found trussed up in the River Odra in western Poland, the police are baffled. The man has been starved and tortured, before being thrown alive into the river. It has all the hallmarks of a punishment beating. The murder investigation stalls until police discover an online murder story written by a Krystian Bala that bears similarities to the death of the man in the river. Bala has even published a book, an explicit cocktail of murder and pornography. Bala becomes the prime suspect

For two years the baby-faced killer Karol Kot terrorised the Polish city of Krakow. Unlike many serial killers he appeared to have no fixed modus operandi when targeting his victims, which made tracking him down difficult. He began his attacks on elderly women, but after a two-year break, he moved to attacking children. An 11 year old boy is found stabbed to death: the boy's internal organs have been punctured in the frenzied attack. A young girl is targeted shortly afterwards. Witness statements link a schoolboy with the crimes. The country is horrified. The killer is finally caught when he confides in a potential partner. His attempt to impress her backfires. Instead she's horrified and goes straight to the police. Once in custody, the schoolboy Kot reveals he drank the blood of his victims as they lay dying.

For over 20 years, sex killer Joachim Kroll had been strangling women across northern Germany. He claimed an internal force drove him, picking women walking alone in the countryside. Many were strangled with their own clothes. Then he molested them. As his killing spree increased, he started to target younger and younger victims. But even this didn't satisfy him. He killed and cooked a cat, which only drove his desire to taste human flesh. His demons overpowered him into killing, dissecting and then eating a neighbour's 4-year-old daughter. But when he was unable to dispose of the evidence, he was picked up by the police. He was charged with 12 murders but admitted to 30, making him Germany's most prolific killer in decades.

Fritz Honka quietly lived in Hamburg's red light district of St Pauli, picking up elderly prostitutes for the price of a glass of schnapps and a bed for the night. He began to lose his temper when the women declined his sexual perversions. He retaliated by strangling his victims. Disposing of the bodies presented a problem until he came up with the idea of dismembering them and storing the body parts in the roof space next to his flat. Had a freak house fire not crept up the building to expose his collection he might never have been caught. He claimed he had been instructed by London's Victorian Jack The Ripper to perform the murders. He was sectioned at a mental institute after being convicted of 1 murder and 4 manslaughters.

Between 1975 and 1983, brutal sex killer Pawel Tuchlin terrorised the region around Gdansk, Poland. Known as 'The Scorpion' for the swift deadliness of his attacks, he targeted women walking alone. Tuchlin struck without warning, felling his victims with hammer blows to the head before molesting their bodies. He killed 9 women and left 11 more gravely injured. But Tuchlin is also a thief: it was his greed and the theft of 4 piglets which eventually led police to his farm, and sent the Scorpion to the gallows.

Anatoly Onoprienko, 'The Terminator', earned his nickname from an unprecedented spree of mass killings in Ukraine. In just 4 months he slaughtered 43 people, entering households and murdering whole families at a time. Children and even babies fell victim to this merciless killer. Onoprienko claimed he was on a dark mission for supernatural powers, that he heard voices in his head telling him to kill. But in reality he killed to make money: his arrogance and avarice led to his downfall as police found over 100 trophies stolen from victims stashed in his apartment. Onoprienko is sentenced for 52 murders, making him one of the most prolific and evil serial killers of the century.