Det. Danny Messer (Carmine Giovinazo) and Det. Lindsay Monroe (Anna Belknap) go to Amity where the Duncan family has been murdered. Sherriff Benson (Robert Picardo, Star Trek: Voyager) meets them at the scene, where he he says they are looking at a father who shot most of his family and then himself. However, it's clear he finds it hard to believe.

Rose, the only surviving family member, is found hiding inside a secret passageway. She is rushed to the hospital for observation and treatment. When she is ready to speak, she tells the detectives a "monster" killed everyone else. Lindsay picks up Rose's drawing tablet to find a sketch of the monster in question.

Adding to the mystery is a house history. Thirty-something years ago, another family was torn apart by murder. Two family members survived and still live in town. Danny and Lindsay use GPS technology to track them down, and arrest both before they can leave town.

The killer is the original family's oldest son, Henry (Seth Peterson, Burn Notice). He and his mother were trying to keep a huge secret. Plans went awry when the Duncans returned early from trick or treating. Henry murdered in a panic.

A zombie flash mob gives an entire new meaning to the term "walking dead" after a man collapses and dies. Det. Mac Taylor (Gary Sinise) and Det. Stella Bonasera (Melina Kanakaredes) team up with Det. Don Flack (Eddie Cahill) to find answers.

Dexter Nevins was buried alive in a scheme to defraud his insurance company. It would have worked, too, if he hadn't woken up and crawled out of the grave.

Mac and Stella learn the doctor who signed the death certificate on Dexter has not shown up for work. They race to his house and find him with Dexter's widow. Neither is dead, but Flack has to get them much needed medical attention.

Can you say evidence overkill? I realize this episode aired on Halloween, but too much happened in the course of an hour to be more than a mishmash of material. Putting Danny in charge of a multiple murder does not ring true. Lindsay, with her history, was also not a good person to send out. She testified against the man who killed her friends, but memories linger. Isn't Mac the head of the team? Speaking of which, I believe Det. Taylor is becoming paranoid. Those phone calls have not hurt anybody, so perhaps it would be best to drop the recurring theme until later down the road.