"The Last Chimera" is the eleventh episode of Season Five of Teen Wolf. It was writen by Jeff Davis and directed by Russell Mulcahy. It is the seventy-first episode of the series overall, and premiered on January 5, 2016.
Scott and Stiles try to learn what is behind the mysterious infection that is killing the town sheriff in spite of their deep rift.
Lydia finds herself wading in a river near a bridge. Dr. Valack is asking her to describe what she finds and to tell him what "he" did. She digs deeper in her dream as she is asked why whoever he is let a girl die. A corpse rises up from the water and grabs Lydia. The corpse is missing a heart and it's made clear that Theo let his sister die in order to get her heart transplanted into him by the Dread Doctors. He was the first step in the direction that the Dread Doctors was going in. Theo is the so-called perfect chimera and it looks like all of this started with him.
Theo's pack of chimera's find Lydia's location and are looking to take her with them. Dr. Valack continues to question Lydia who recounts the entire episode 10. The sheriff is being rushed into the emergency room and all he can do is ask for Stiles who is busy getting the insurance information set. Scott's mom tells Stiles he will be there as soon as he can but Scott seems to be in worries all of his own. He is staring into a mirror in pain and anger with his eyes glowing red. He patches the wound in his chest and grabs his motorcycle helmet to take off but something happens. He begins to stumble in a daze and passes out on the floor.
Stiles is nervously waiting to hear about his dad and seems extremely distraught. Parrish is taking a shower which is washing off all of the soot and grime from the fire he rescued the last chimera from. The only thing is, Lydia happens to be in the shower with him and the two of them begin kissing passionately. Parrish notices that Lydia's fingernails are off and he asks her what's going on. She tells him he is a harbinger of death and someone is dying. Parrish wakes up and calls Hayden's sister to inform her that Lydia is missing. She tells him that he is missing and people are starting to wonder about his behavior.
Parrish is searching for Lydia in the woods and decides to spark up a flare to help him. It triggers his power and his eyes start glowing as he drops the flare. Scott's mom tells Stiles that his father is going to be just fine and he is crying tears of joy. Meanwhile, Scott is laying facedown on the floor but Parrish of all people happens to find him. Parrish says that he needs Scott's help with Lydia who looks as if she is in a trance. He tells Scott that Lydia wrote a sheriff's badge in blood and Scott realizes that it is a warning. Is it possible that the sheriff is going to die?
Hayden's sister is taking off in her car and Liam wants to go after her to tell her that Hayden is dead. Mason convinces him to stop and think about it. He says the news won't hurt less coming from him. They both get up to move but something happens with Liam. He senses Hayden's scent and he tells Mason that she is here. Mason tries to convince him that Hayden is gon but her image appears in a car window. She turns away and Liam is left confused.
Parrish and Scott rush Lydia to the hospital and Scott takes the time to go see how the sheriff is doing. Stiles is freaking out over his dad because no one can give him an answer to what is happening. Stiles breaks through the door and attacks Scott. He asks him where he was and has to be pulled off of Scott. Scott tells him that his dad isn't the only one that got hurt. Lydia is being watched over by her mom when Stiles walks through the door. She doesn't want to see him or listen to him when he tells her he may know who hurt Lydia. She pushes Stiles out of the room and slowly walks over to Lydia who is still in a daze. She spots a wound on the back of Lydia's neck.
Stiles, Parrish, Scott and his mom are trying to figure out why Theo is targeting Lydia and the sheriff. Stiles tells them he is going to go meet him alone and that he doesn't need to look. Theo meets Stiles with a smirk on his face. Lydia's mom has had her transferred to another facility when Parrish walks up to her. He asks what she did and she tells him she did what she had to. Stiles tells Theo that he killed his best friend and wants to know why he poisoned his dad. Scott happens to be listening on. Theo tells him he knows what the Dread Doctors created and he knows what Parrish is.
Liam and Mason are being sent home from the hospital but they aren't going home. They set out to find the Nemeton so that they can find Hayden's body. Scott listens on as Theo says that Lydia was collateral damage. Stiles attacks Theo and asks him what is going on with his dad. Theo pushes him back to the step and he passes out. The voice of his dad wakes him up and Scott is there to help him up. The two realize that the sheriff wasn't attacked by Theo, he was attacked by another chimera.
Stiles is ready to leave and denies Scott's help. Stiles tells Scott that he doesn't know the whole story but Scott says all that matters is his dad and that together they have survived worst. Stiles says they aren't looking for a missing chimera, they are looking for a missing teenager. Mason and Liam are back at the library where the showdown between Theo and Scott took place. Liam is reliving it all when he is interrupted by Mason. They open up a book with a map that shows an intersection for the Nemeton. Liam lets Mason know that in order to find the Nemeton it has to want to be found.
Parrish tells Lydia's mom that he is going to find a way to get her out the institute if he has to break the walls down. Dr. Valack happens to be the one who took her captive. Stiles and Scott find an article of clothing that will lead them to the missing teen and Malia joins them in the search. Another teen is being chased and is forced to hide from his pursuer. Liam and Mason are at the site of the intersection but they don't see a clearing. Liam is still upset that he couldn't save Hayden and he also feels bad about attacking Scott. Mason tells him it was about losing Hayden, the fear, the anger and the fact that Theo took advantage of him during the super moon.
Just then the conversation stops and Mason says that it could take a supernatural creature to find the Nemeton. He tells Liam that he he was looking with his human eyes and when he looks with his wolf eyes, he finds the Nemeton. There are also a few chimeras laying at the base of it. Malia and Scott are at the site where the teen was running from his pursuer. Scott is trying to talk to Malia about what has been going on with her but she tells him not to ask her to talk. She suddenly gets a scent of the teen and the three move onward.
The doctors including Scott's mom have no idea what is going on with the sheriff and she instructs them to keep him alive for as long as they can. Mason and Liam are trying to find out if Hayden is alive when a unit of police accompanied by Hayden arrives. She tells the police that this is the location where she found all of the bodies. Liam has the look of utter shock on his face. While Scott, Stiles and Malia are trying to figure out where they still need to look, he passes out once more and his dad guides him back. Malia grabs the teen and holds him down but he begs her to let him go. He tells her that "they" are coming and by they he means the Dread Doctors.
The teen tries to run and Stiles stops him and questions him about the attack on his dad. Scott tells Stiles to take the boy with him and figure out a way to help his dad. Malia and Scott are about to come under attack by the Dread Doctors when Chris Argent returns. He saves them with a few shots towards the Dread Doctors. Stiles and the teen reach a point where they can't go further. However, the teen uses his chimera powers and is able to break through the gate to help them escape. Scott's mom reveals that the sheriff is being poisoned by a piece of bone marrow and the doctors begin operating to save him. At the end of the episode, Scott, Malia and Chris walk into the hospital to greet his mom. The sheriff is alive and wakes his son up to tell him it's okay and he still has him.Theo and Hayden are retracing the tracks of the teen who is half jaguar and half berserker. Hayden says she thinks he is dying and Theo realizes that the Dread Doctors are going to find the teen and probably already have. Theo traces on further and realizes he could have used the chimera. He looks up and sees the sign of an alpha from Scott's pack. Theo and a couple of his chimeras attack Dr. Valack and he makes his way over to Lydia. He instructs the chimeras to pick her up and get her out. Theo says he is looking for a hellhound and just then Parrish is shown in flames, anger and melting the cage down. Parrish is a hellhound.