Obsession

The case of 17th-century serial killer Erzsebet Bathory - a Hungarian aristocrat who is said to have murdered 600 of her servants in an attempt to achieve eternal youth

Greed

The cases of Belle Gunness, who murdered her victims to reap financial rewards, and a carer from Connecticut who turned a home for the elderly into a death parlour

Revenge

The stories of notorious killer Katherine Knight, an Australian who skinned and decapitated her errant lover, and Blanche Taylor-Moore, who poisoned her partner in hospital