Crimson (aka Las Ratas No Duermen De Noche)

Horror co-written and directed by Juan Fortuny and starring Paul Naschy, Silvia Solar and Gilda Arancio. When a jewel robbery goes horribly wrong and their leader Jack (Naschy) is shot in the head, a group of criminals go to extreme measures to save their friend's life. With the help of a local doctor, the gang devise a uniquely gruesome plan - to kill their worst enemy, throw his body in front of an oncoming train and use the brain from the severed head as a transplant.

The operation is a success and all seems well - until the body's former owner starts living out his murderous past through Jack, turning him into a madman bent on death and destruction.