The latest “Teen Wolf” episode was a rescue mission. The pack knew that they needed to get Lydia (Holland Roden) back, but in Season 5B, episode 15, they learned that she was in danger. They couldn’t let Lydia die, so it was time to invade Eichen House. However, helping a banshee escape from a mental institution that houses supernatural creatures is no easy task.

Episode 15 starts with the police following the Beast of Gévaudan, and of course, Stiles (Dylan O’Brien) and Scott (Tyler Posey) are right behind them. They realize that the Beast is headed for the hospital. Melissa (Melissa Ponzio) is evacuating all the patients when the lights start flickering. She runs out to follow everyone else.

On the police radio, there is a report of a man on fire running into Beacon Memorial. The Sheriff (Linden Ashby) tells his deputies to disregard that, and Stilinski, Scott and Stiles handle it. The hospital is in shambles with debris and small fires everywhere. They see Parrish (Ryan Kelley) suddenly thrown across the room. While that isn’t a good sign, he did survive and the Beast ran away. That’s more than all of his other victims can say. Scott looks at the bloody footprints on the floor. They quickly go from an animal-like paw to a normal sneaker imprint.

Later, Deaton (Seth Gilliam) shows Scott and Stiles photos from Dr. Valack’s (Steven Brand) previous tenure at Eichen House. He experimented on supernatural creatures. They see a photo of a banshee who died while screaming. If Valack does the same to Lydia, it'll be too much for her since her powers are already stronger than that of the average banshee. “Putting a hole in her head will be like putting a leak in a nuclear reactor,” Deaton says. The banshee isn’t the only one in danger. Lydia’s own dying scream could be enough to kill everyone around her.

Stiles goes to his father and find out that there is nothing he can do for Lydia … legally. Illegally is another story, so Stiles comes up with a plan. They need to trigger a brown out to reset key cards, and Stiles can use the card he stole to get into Lydia’s ward to save her.

At Eichen House, Valack shows an orderly a Dread Doctors’ helmet. She asks him if it actually works, and Valack decides to test it on her. She flails around in pain, and suddenly stops. It isn’t clear what happened to her, but it can’t be good.

At school, Kira (Arden Cho) has to learn how to use her powers to create a brownout. If she creates a blackout, she’ll trigger a full lock down. She never really learned how her powers worked, so it’s a difficult task. She only manages to make a lot of lights explode while practicing with Malia (Shelley Hennig) in an empty classroom. Once they leave, Corey (Michael Johnston) pops out of the wall. The invisible chimera was spying on them for Theo (Cody Christian).

Scott and Stiles run into Theo in the library. The chimera leader claims that they need his help. The chimeras can get past the mountain ash — Scott’s pack can’t (except for Stiles, a human). Theo believes Lydia can help defeat the Beast, but they don't want his help.

Meanwhile, the Sheriff tries to convince Lydia’s mother (Susan Walters) to get her out. Mrs. Martin refuses to believe in the supernatural. He shows her a file with the same photos Deaton showed the boys. He hopes he can convince her to take Lydia out of the mental hospital, but he isn’t counting on it. Stiles and the pack go ahead with infiltrating Eichen House.

Parrish stops by Eichen House in a sheriff’s van with a morgue delivery. The security guard makes him open the body bags, but luckily, Parrish has one decomposing body with him. That’s enough to convince the guard, which is good since the other body bags have Scott, Stiles and Liam (Dylan Sprayberry).

Malia has one of her friends from her time at Eichen House distract the receptionist by streaking so she and Kira can access the electrical room. Kira, who never actually managed to create a brownout while practicing, gets nervous. Malia tells Kira to stop worrying about what she is doing. They have to save Lydia. Kira manages to cause a brownout.

The other parts of the plan don’t go so well. The door Stiles needs to get through no longer has a key swipe. Scott and Liam try to breakdown the door, but it doesn’t work. Liam decides that they’ll have to get angry. He has Scott think about how his beta recently tried to kill him. Liam makes Scott start punching him, and they both get angry enough to break down the door.

Unfortunately, it seems chimeras will ruin their plan. Tracy (Kelsey Chow) attacks a guard outside. The chimeras walk in the front door and attack anyone who gets in their way.

They don’t bring everyone with them, though. Hayden (Victoria Moroles) stays with Deucalion (Gideon Emery), who is being held hostage. He offers information on the talons Theo got from the Desert Wolf in exchange for his freedom. He says that Theo will never be able to use the talons. They’re made for a different chimera, so his body will reject them. Putting on the talons will kill him.

Back at Eichen House, Stiles finally gets to Lydia. She tells him that the pack will die if they stick around. She wants him to leave her behind, and he has to. Dr. Valack is on his way over.

It seems everyone wants to get to Lydia tonight. Mrs. Martin needs to see her daughter after reading the file the Sheriff gave her. She finds a dead security guard at the front gate.

Inside, Stiles leaves Lydia’s room, but he listens to Valack’s interrogation. Valack asks if the pack is back together yet. Lydia says someone is coming, and it isn’t Scott.

The alpha can’t come to her rescue because he and Liam are stuck outside the ward due to the mountain ash. The chimeras, however, easily walk in. Tracy grips Valack by the throat, and Theo clarifies that he doesn’t want Lydia after all.

“I don’t want a Banshee. I’m looking for a hellhound,” Theo reveals. Luckily, Parrish sensed something was up and turned the car around. He appears in Lydia’s room, and he is on fire.

Theo may have met the man he wanted, but it isn’t clear how any of them will be able to get out of Eichen House. The building is sent into lockdown. This prevents Lydia’s mother from entering and the pack and chimeras from leaving.

Four guards attack Scott and Liam with tasers. Everyone’s powers seem to be triggered by the lockdown, though. Scott and Liam are suddenly strong enough to fight off the guards. “Come on, we’re getting Lydia out of here,” Scott says. Fans will have to wait until next week to see if they can actually complete the rescue mission.

“Teen Wolf” Season 5B airs Tuesdays at 9 p.m. on MTV.