A murderer makes his escape on the night before Halloween.
The murderer killed kids because they had glowy eyes.
Aiden and Ethan go to Scott looking for a pack and an Alpha. When he turns them down, they decide to go back to high school.
It's coach's birthday and Mischief night. They play pranks on him AND give him a birthday present, which he smashes with his foot.
The murderer, Barrow, is in surgery while Lydia hears flies, just before they burst out of his stomach, he kills people and make a run for the school.
Derek sews Peter's finger back on just before showing him what's in the container they retrieved from ash - Talia Hale's wolf claws.
Stiles tells his dad about Lydia being a banshee, but he prefers to listen to eyewitnesses instead of banshee.
While everyone is on lockdown, Scott goes to Kira's for dinner. They serve sushi. Mr. Yukimura wanted to impress Scott, who couldn't use chopsticks.
Lydia starts to doubt herself when they don't find Barrow at the school. Stiles tries to give her some confidence.
Peter and Derek continue their ritual with Talia's nails when Peter plunges them into Derek's neck.
Scott through the wasabi was guacamole and ate it all.
While investigating at the school again, Stiles realizes Barrow was at the school performing surgery on himself. They look for clues and find atomic numbers. Potassium, Iodine and Radium, which spell KIRa. Barrow wants to kill Kira.
Derek finds himself in front of a vision of the Nemeton with his mother's wolf standing upon it.
Isaac tries to kiss Allison and she tells him he's crazy if he thinks she's ever kissing another werewolf. So he stands up and takes his shirt off and she counters. Then her dad walks in.
When Scott leaves Kira's house, Barrow jauntily runs up behind him and whacks him in the head so he can take Kira.
Stiles and Lydia find Scott and Lydia uses her Banshee power to figure out where Barrow might be.
When Barrow tries to electrocute Kira she does something that captures all of the electricity and rises up while absorbing it into her arms. The city goes dark.
Back at the Argent house, Isaac is trapped in a darkened room with black bodies, masked and robed, swarming around him.