Luther takes down one of its few remaining longstanding characters, as DCI Luther's problems mount.
Mark: I see you brought the devil 'round for breakfast.
The things about Luther as a series is that, by this point, it's kind shocking its titular lead isn't dead or in jail by this point. The man never follows the rules, he's always trying to hide his connections to killers (Alice Morgan, George Cornelius), and he makes terrible, stupid mistakes by trusting people he has no business believing. Episode 3 opens with Alice having killed Cornelius' kid, which is going to go very badly for everyone when he finds out. Especially because Cornelius has Benny. As I noted back at the top of the season, Benny is literally only one of two characters besides Luther himself, who has lasted through all five seasons. Even Alice sat out the truncated two-part Season 4, in what we can admit was a (failed) attempt to kill the character off and see if the show could survive without Ruth Wilson.
Luther seems to be either bringing Alice into the station or is en route to giving her up to Cornelius (who doesn't yet know his son is dead), but once again he cannot go through with it, because they are just the weirdest couple who ever lived, and besides it's not like she can kill him either. These two will be together until the end of time, or both of them dies, one of the two. Either way, things are not looking great for Benny's future, even as the two of them race to free him. Alice provides the distraction, setting the warehouse where Benny is tied up on fire, while Luther goes in and gets Benny out. Cornelius is annoyed and decides to go to Schenk to demand Luther be dealt with. Schenk basically responds that whatever happens to Luther is Cornelius' business, but if he touches a hair on Benny's head, the entire police force will come down on him.
And that's when Cornelius finds out his son is dead, and the entire game changes.
Unable to go home, but without the ability to stay where he is, Luther goes to perhaps one of the most surprising locations to try to stash Benny and Alice: Mark's house! Hello Paul McGann, it's been a whole minute since we've seen you, and by a minute, I mean since Season 2. Mark, bless his heart, opens the door, and lets the whole gang inside. As long as they don't drink all the OJ, don't get blood on the sofa, and are out before his wife gets home, he'll allow it.
While Luther's world is basically falling down around his ears, over with our secondary killer storyline, Jeremy is trying to make up for the horrible things his wife Vivian had to do to cover for him. She debased herself in front of cops,throwing away their contingency psycho to cover his tracks. Vivian hopes that Jeremy understands that the risks he's taking are too much, because they've put her in danger, but clearly the answer is no, since Jeremy is hoping that a new victim, Penny will patch things up between them. Somewhere in his mind, he thinks they could share her together; it's a great surprise he brought home! But once the answer is obviously going to be no instead, Jeremy drugs his wife, because that's an entirely healthy relationship, and brings in his new plaything to tie up alone.
Let's hope Jeremy is taking tomorrow off because when Luther finally checks in with Halliday, she's on her way to do something stupid. Since Luther can't exactly come into the office, considering he has both Alice and a beat up Benny in his possession, Halliday chirps that she's off to look into Jeremy's files alone. Without a warrant, but she'll make it work! Tim Gunn would be very proud of how Halliday makes it work too, getting someone to call the secretary so she can be Little Miss Momentary Interruption, and oh just let me pop in and find my glasses and thank you kindly administrative assistant who is so busy with her phone call! Not only does she efficiently ransack the place for evidence, and turns up an MRI Jeremy was obsessing over when they were there the day before, she even agrees to cover for Luther's absence as well. Halliday has no idea what she's dealing with on any side of her case.
The MRI that Halliday turns up apparently has a tumor in it, marking the owner of that brain as a very sick person indeed. Symptoms, in case one hadn't guessed, are loss of self-control, and once the Missing Persons call comes in for Penny, the woman Jeremy took, and footage of him in her building's elevator, the case is back on. Luther will have to go in, leaving Alice and Benny unprotected.
Jeremy does make it to work after Halliday has been and gone, but he's not there for long. Vivian wakes up and discovers Penny in the basement. Jeremy might have raced home to deal with the issue, but Schenk, Luther, and Halliday are already walking on in. Meanwhile, back at home, Vivian is cleaning up her husband's mess, again, when Luther turns the entire crowd around and heads to the Lake's house and interrupts. Penny is saved, and Vivian is arrested. Jeremy is now untethered and on the run.
But there's no time for Luther to chase him down, because Cornelius's assassin-for-hire, bent on revenge, has made his way to Mark's house, and is demanding Luther's immediate return. He also got blood (and brains) on the couch: Benny's. Sorry, Benny, you had a good run. Schenk's going to be very disappointed when he finds out Cornelius didn't stick to their agreement.