"The dead don't come back. We think they do, but they don't."
These are the words of DCI John Luther (Idris Elba), spoken at the tail end of the tantalisingly brief fourth season of Luther right before Christmas.
In season one, Luther introduced us to Alice Morgan, a child prodigy who killed her adoptive family in cold blood. Equal parts charming and dangerous, she was the closest thing to a '40s femme fatale on television, a character so deliciously antagonistic that every time the show returns, Alice dominates the conversation.
Season 4 acknowledged the audience's love for the character by bringing her deep into the heart of a fresh mystery: Alice's apparent death.
We know from experience that off-screen deaths are rarely what they seem, especially when it comes to a character like Alice, a known master of deception. Killing her would be bold but, sadly for us, it would probably kill Luther itself in the process.
It's for this reason that now, four seasons in, Luther finds itself at a crossroads.
Speaking to The Hollywood Reporter last year, Elba mused on life after Alice:
I don't think viewers are going to be satisfied that she is dead, or that Luther thinks she's dead, either. [But] I think the world of the show exists and continues. But that said … and I'm not being deceptive or anything, but the truth is, John Luther isn't quite sure that she's dead! (Laughs.) You know?
Neil Cross, the show's creator, has always been vocal about the possibility of transferring Idris Elba's maverick cop to the silver screen. For John, a character without parallel on television, a movie seems like the logical climax to his journey.
If Alice truly is dead, a movie could function as a kind of rebirth: the series is chapter one, every few pages punctuated by a reference to the red-headed murderess who has an odd grip on John's heart. The movie is a clean break.
Season 4, though, did not kill Alice.
By engineering her death as an off-screen plot device, Cross plants that seed of doubt. He knows that the audience's investment in the show revolves heavily around the prospect that, one day, Luther and Alice can find some way to live together (or even die together) in a bizarre kind of symmetry.
Elba also spoke to THR about a potential season 5.
I'm far from done. He's one of the characters that I love and have some say in where he goes. That's enjoyable as a producer. I don't see myself turning my back on it. I think there are various ways of dissecting Luther, from theatre to film. I don't see why not.
Unlike some critics in the UK, I thought season 4 found Luther on pretty good form. Purely for the joy of seeing Idris Elba rampaging through the streets of London in his incredible coat, I will always be game for a new series, or a movie, or whatever else Cross wants to do with the character.
But all good things come to an end, and should season 5 come to fruition, the show might want to find a way to shake off Alice's spectre.
After all, the dead don't come back. We think they do, but they don't.