A deranged serial killer called Mister Sleep, survives prison execution and is reborn as a terrifying and unstoppable force of nature who unleashes savage and bloody revenge on a group of insomnia patients participating in a new drug trial - a group who he believes have stolen his memories. His relentless thirst for revenge sets him on a collision course with the man who sent him to death row and his young daughter, who is part of the group testing the new medication.