Sanity is very rare. Every man almost, and every woman, has within them a dash of madness.

An aura of mesmerizing evil hangs over mid-winter central London in the guise of “the Twilight Strangler” a particularly insidious serial killer who’s busy strangling professional women on their way home from work during the city’s fading light hours.

One woman seemingly unconcerned by any danger is vivacious and effervescent office worker Callan O’Dowd. In a desperate attempt to provoke a reaction from her much coveted erstwhile beau she hones her attentions in on, and begins to aggressively pursue, her desperately shy and disturbingly aloof office colleague Justin.

Unfortunately for Callan, she is not privy to the thoughts inside Justin’s mind and as we bear witness to him fantasizing about murderous attacks on the same young woman slain by the Twilight Stranger we’re never actually certain if we’re watching the morbid daydreams of a bored young office worker or witnessing the inner world of the real compulsive killer reliving his crimes over and over again in his mind.

Unaware of what’s lurking in the deeper recesses of Justin’s head, whether they be the truth, a lie or a dream, Callan begins what at first is a thoughtless game but gradually becomes a dark fascination and gradually a creepy symbiosis ensues. She finds herself increasingly intrigued by the introverted near-silent boyish man – drawn in by his “wild thing of the night” mystique and the sullen mesmerising presence at his dark heart. As they close in on each other Justin proves an addictive alternative to the lackluster men Callan is used to, especially when he begins taking her on tours of the stalking grounds of killers and regaling his grisly knowledge of local murders in encyclopedic detail.

This new macabre hobby fills Callan’s voided social life and begins to overtake the other half of her life as well, Justin having ignited an unsettling dark flame in her that had obviously been burning slowly and quietly until he came along, and as the lustful pair embark on a wild ride of dark passions they progressively begin to merge personalities.

The deeper the couple descend into debauchery the more Callan’s psyche begins to crack and her grip on reality slips further out of reach. From there on in her world only gets both odder and more schizophrenic as career and once solid friendships hang in the balance. With Justin completely under her spell she comes dangerously close to finding out how easily the two of them could turn their dark fantasies into a cold-blooded reality.

However one ominous hour of dark reckoning jolts Callan back to her senses and she realises she must try to salvage what’s left of her life if she still can.

Unfortunately for Justin, he is by now utterly in love with Callan and, having allowed himself to feel the warmth of a woman’s desire and the taste of physical love, considers himself a complete human being for the first time. And so Callan’s sudden rejection, combined with the mentality of his newfound friends, as quick to unilaterally condemn him as they were to adore him, is more than his soul can bear and he spills out into the city streets, his loneliness and longing erupting into irrational rage and what culminates is one very dark night of the soul where Callan sees no danger until it’s too late and the realities of Justin’s mind are finally revealed.