On the surface, Sofie (Julie Zangenberg) and Sebastian (Sebastian Jessen) are an ordinary teenage brother and sister. If there were anything unusual about them, beyond a certain hypnotic charm, you would need to get very close before you would find out what it is. And you would regret it, because Sofie and Sebastian are energy vampires (although, in this universe, they’re known as ‘suckers’. The word ‘vampire’ is never used). In a single kiss they can suck the life-essence out of you. And if they drain you too much, you will erupt into flames.

But Sofie and Sebastian aren’t just hungry for energy. They are orphans, desperate to find out who their mother was, why they are doomed to live this life and if there is any way they can ever become normal. Their quest brings them to the Ottman boarding school; an impressive gothic estate where sadistic prefects oversee twisted initiation ceremonies and where proficiency with the fencing sword (there are some fantastic fencing sequences during this series) is seemingly more prized than academic ability. The Ottman School has a dark history involving a vengeful ghost and the burning of witches and Henrik Just (Nicolaj Kopernikus), the Ottman’s principal, has a nasty secret of his own. To make matters even more complicated, one of Just’s three daughters is also beginning to exhibit psychic abilities that would put Stephen King’s ‘Carrie’ to shame.

From the moment they arrive, Sofie and Sebastian are not only in the midst of danger; they are stirring up the hormones of their fellow students. It’s a potent mix because, as in all great horror stories (especially vampire ones), the sex and death in ‘Heartless’ are always very close companions. But there’s more. The hunters are coming, and if Sofie and Sebastian can’t solve the mystery of their birth right before their vampire identities are discovered, they will certainly be destroyed.

How are Sofie and Sebastian connected with the Ottman School and its violent past? What was their mother looking for when she came here and then mysteriously disappeared? What is the heart of gold, and who else is looking for it?

‘Heartless’ is the most seductive, fascinating slice of television gothic this reviewer has seen for quite a while. Don’t be deceived by the teenage leads and boarding school setting, ‘Heartless’ is much darker and more adult than its ‘Buffy’ meets ‘The Vampire Diaries’ premise might suggest. In fact, Sofie and Sebastian’s energy vampirism gives us a big clue as to this series’ originality. On paper, energy vampires might not sound too exciting – after all, how can sucking the lifeforce from a victim ever be as visual (or visceral) as sinking fangs into the victim’s neck? – Well, watch the opening moments of episode one and you will be left in no doubt, ‘Heartless’ had the potential to be something very special. 

And there’s the crux. ‘Heartless’ was produced by Danish broadcaster Kanal 5 – yes, it’s subtitled but don’t let that put you off – in the hopes it might enjoy the success of recent Danish TV triumphs like ‘The Killing’ and ‘Borgen’. Unfortunately, although viewing figures started promisingly they plunged pretty quickly, and after the initial run of five episodes ‘Heartless’ was cancelled leaving the story unresolved. Thankfully, audience outcry was so great that three further episodes were made to give ‘Heartless’ a proper ending and – who knows – even suggest where a spin-off series could go if some brave producer ever takes it on.

So let’s keep our fingers crossed. If the international reaction is strong enough, there may be more life in these teen vampires yet. But for now, don’t miss ‘Heartless’ on C4’s new international showcase Walter Presents. I’m already willing to bet it will be one of the television highlights of 2016.

Heartless is available as a free box set exclusively on All4.com/WalterPresents.

HEARTLESS: SEASON 1 / CERT: TBC / DIRECTORS: NATASHA ARTHY, KASPAR MUNK / SCREENPLAY: VARIOUS / STARRING: JULIE ZANGENBERG, SABASTIAN JESSEN, NICOLAI KOPERNIKUS, ALLAN HYDE / RELEASE DATE: VOD OUT NOW