Good drama deals in empathy. It’s about characters we care about being put under pressure and forced to make choices that go to the very heart of who they are. In the first season of 24, Jack Bauer is torn between saving his family and saving the world. Tony Soprano constantly balances the tension of the choice between being a good man or a powerful one. And because we understand the consequences, we’re there for every step of the ride. Empathy.

The amazing thing about Dexter (Thursday, 8:30pm, Showcase) is that its moral universe is so far from our collective experience that it could almost be called inhuman. And inhuman doesn’t normally go with empathy. We can empathise with anything as viewers – animals, insects, even inanimate objects – as long as they display recognisably human characteristics. But Dexter is dangerously close to being so psychopathic that he’s barely human at all.

Dexter, you see, is a serial killer. Police blood spatter expert by day, by night he indulges his compulsions by tracking down and murdering the baddies who slipped through the crime-fighting net. He’s fortunate, really, in that he had a cop father who recognised his urges early on and channeled them towards vigilante justice rather than random slaughter. But still, he’s a murderer.

Not that a murderer is necessarily impossible to empathise with. Tony Soprano knocked off his fair share of people, some of whom really didn’t deserve it, and we were still on board with him (even if we hated ourselves for it). Because in Tony we saw the fallibility of humankind. We empathised.

Dexter almost prides himself on his complete dislocation from human emotion. He murders without remorse. He has a girlfriend who he appears devoted to, but his voiceover tells us he is faking everything. Every laugh, every hug, every gesture of affection. His performance, he brags, is so humanlike that no-one can tell the difference.

But that’s the thing – it’s a performance. It’s very tough for an audience to empathise with a character who doesn’t empathise himself. Dexter’s emotionless murdering is strangely compelling, but without that emotional tension, viewers will begin to wonder why they should care.

And that is the challenge for Dexter. How to make an audience feel empathy towards a character who is, by his own admission, barely human? Well, in the first couple of episodes there have been some beautifully-judged hints that suggest Dexter might not the reliable narrator he thinks he is. That perhaps he feels just a little more than he lets on.

And an inhuman serial killer battling unwelcome human feelings? Now that’s a cracking yarn.