Five-0 deals with a mob contract killer who has literally and figuratively had a change of heart. Danny finds his brother's money but is short five and a half million dollars, and his brother's life may be in the balance.
It's Halloween and Five-o must track down a serial killer who is copying murders depicted in a cult slasher film. Meanwhile, McGarrett must help Jerry after he is kidnaped by the counterfeiters he has been tracking.
Danny and Chin Ho are arrested for the roles in the death of Marco Reyes, the Columbian drug lord who killed Danny's brother. But with the help of Joe White, McGarrett discovers that there's more to their arrests than meets the eye.
McGarrett and Odell come under siege in Odell's barbershop when they try to protect a man who is being hunted by a gang. Meanwhile, Jerry is wrongfully accused of committing a series of home invasions.
Grover's closest friend's wife is killed on their anniversary trip to Hawaii, but Grover suspects that he may have killed her. Meanwhile, Danny is stuck in an elevator with a dead body and a medical examiner.