After a slightly disappointing outing last week, Being Human is back on form with the strongest episode of Series 4 yet.

A Spectre Calls, appropriately, sees a Seventies ghost named Kirby turning up at Honolulu Heights. He was a nursery teacher before his untimely death, apparently, and claims to have been sent by Nina to help with baby Eve. Of course, it doesn’t take a genius to realise that something fishy is going on and soon enough it’s clear what he really has in mind.

Although the housemates are suspicious of him at first, Kirby is able to quickly work his way into the group and proceeds to test how strong the housemates’ relationships with each other really are.

James Lance is the star of this episode and gives a brilliant turn as Kirby. He’s clearly having a lot of fun playing the unhinged character. Kirby comes across like pre-school teacher talking to characters like lost tots. Really, he’s a master of manipulation playing them like fiddles and loving it. When he tells Annie, “I don’t mean to cause any trouble between you guys,” shortly after a round of stirring, you just wish the housemates would wake up and realise what’s really going on. Only Hal is wise to his antics, but even that doesn’t last.

Kirby goes through each of the characters exposing and exploiting their foibles: Tom’s naivety and the lost little boy inside; Hal’s inner demons and fight with his vampiric bloodlust; and Annie’s loneliness and insecurities; all are used to turn the housemates against each other. In doing this, he gives the three lead actors a chance to shine as he brings out their best and worst qualities.

While the majority of the episode is centred on Kirby, there are a couple of other interesting plot movements going on in this episode. The “Box Tunnel” murders make a surprising return when a new development hits the headlines again. Hal turns into nastier version of Sherlock when he follows up on it.

After his absence last week, Cutler (Andrew Gower) is back and makes an surprising move towards one of the housemates. We also learn the identity of the person with the burn at the episode’s conclusion, though you can help but feel this is a red herring at this stage.

Being Human has always been, at its core, a character drama and this episode illustrates where the show works at its strongest.