DCI Luther's run of good luck covering himself finally comes to a screeching halt as Luther Season 5 ends.
Luther: Take it, an eye for an eye.
One can understand why Luther is a little bit gunshy about letting people or work colleagues get close to him. Ever since the first season, everyone around him seems to get killed. Everyone, that is, except Alice. This might explain his attraction to her, as the only survivor next to him, at least he knows as long as she knows how to kill, she'll always stay alive.
Everyone else is not so lucky. Benny got his head blown off at the end of last week, and the professional assassin, Palmer, who took him out is only promising to leave Mark alive if Luther does exactly as told. This is already a massive problem since Luther is supposed to be dealing with serial killer Jeremy Lake, who is currently on the loose. Instead, he's now being forced to run a rat race through a series of checkpoints to keep at least one innocent person alive. (Alice doesn't count either as an innocent person or as someone planned on being left alive.)
While Luther is otherwise occupied, Jeremy just picked up his next quarry, who is shortly strung up under a bridge, drippingly dead, with a mask of Lake's own face on it. Unfortunately, Luther can't pay attention to that now, and he's made the mistake of pulling Halliday in to find Ronald Massey, George Cornelius' assistant. As has been demonstrated all season, Halliday is far too quick to put pieces together to risk this, and yet here we are. Halliday tries to tell Luther this won't fly, especially with Schenk practically livid over Luther's disappearance.
Turns out Halliday's pinpointing of Massey is enough for Luther to skip the checkpoint run and go straight to the top boss, forcing Cornelius to call his assassin off. (Palmer is not pleased since he already killed Benny.) Luther admits he came planning to kill Cornelius in revenge for Benny, but he doesn't have it in him. So instead, he hands the gun to Cornelius and tells him to pull the trigger. Turns out Cornelius doesn't have that in them either, so the two of them gang up on Palmer, where Cornelius frames Luther for shooting the guy dead and leaves Benny's body nearby to be found. They're even, for now, as long as Cornelius has that on Luther to keep him in line. At least Mark and Alice are alive when he finally pops into the freezer where they're being held. Well maybe "at least Alice is alive" is not the correct way to frame it, as this means she's alive and George is alive and one of them probably won't be soon enough.
And that's when Schenk finds out Benny is dead, and the entire game changes.
Luther finally coming into work means that viewers get to see for the first time this season what makes him a good cop, as he and Halliday break down Jeremy's wife, Vivian, in the interview room. The game he apparently liked to play was "happy family," involving having people summoned to him like lambs to the slaughter. He's clearly playing it again, taking over the flat of the poor school teacher from the season premiere, since he can't go home, but he wants a place the cops would guess as meaningful. (After all, that's how Luther was first alerted to his whole game, was when the boy following said teacher home made the mistake of looking in the wrong window). First victim, a plumber to fix the pipes, but that's only the beginning.
Meanwhile, Schenk has tracked down enough evidence to tie Benny's murder to Cornelius. And ehee gets there just in time to take the gangster out. Another thirty seconds and Alice would have mowed him down with the machine gun she's weilding outside his windows. Cornelius' survival means he can show the framed images of Luther standing over the assassin's body, proving he has been lying about both his recent whereabouts and his ignorance regarding Benny's disappearance. Schenk calls Halliday to bring Luther in on the sly. Luther doesn't need to pretend he hasn't already guessed, but he's damned if he'll head back into the office to give himself up before taking out Jeremy.
Taking out Jeremy doesn't take that long either, it turns out, once Luther uses Halliday to draw the creep out. With a full ten minutes left in the episode, Luther has time to run from Schenk, and Halliday won't stop him. Except before he can go, Alice pops out from behind a car and shoots Halliday in front of him. It's a lesson, how Luther uses people and then leaves them to die, how he's lied and lied and covered up, and now there's nothing he can do. Halliday is dead. Alice falls to her death as Luther tries to arrest her. Luther is once again framed for it, just like when the story began back in Season 1 with his wife, Zoe. Alice got him out of that.
Now she lies dead, and there's no escape. Schenk takes him in.