It was always going to be the elephant in the room – one of the acclaimed comedy sketch group's three performers isn't there. So the first thing they do is to shoot the elephant, metaphorically speaking. New boy Adam is going to play the missing "Jim", but he's not welcome, and he shouldn't get too comfortable. It's true Gein's style: this is an enjoyably aggressive and dark collective, and to be nice to each other would go against the grain.

Gein's Family Giftshop manages to combine both individual sketches and something of a narrative arc; Kath and Ed stay in whimsical horror character, chaperoning us through the hour. They turn on a sixpence between endearingly sweet and marvellously despicable, trampling on taboos with gay abandon as they go. You've never met such likeable psychopaths. The sketches and links slip into one another fluidly, never letting you stop to wonder what will happen next – it's simply happening. And that works particularly well with their brand of left-field punchlines, that hit from out of nowhere.

Volume 3 is skilfully written, never flinching from the gross or the wrong, and in some cases – most noticeably in a sketch involving airport security – actively seeking it out. They move in the minimum number of steps between laughs and the unexpected, and keep the element of surprise on their side: punchline-topper follows punchline-topper just as the audience think the sketch has come to a close. It's a neat trick, and keeps the laughter building when it might subside.

But there are tense moments too, in which you could hear a pin drop. One example can be seen during the bullying of poor Adam, who adds a different dimension to the dysfunctional dynamic than the wannabe alpha-male Jim did. It was a wise move to recruit someone so clearly different, as Adam's contained obedience and educated Southern tones slot him into the group at a brand-new underdog level, a fact they play with like wanton children.

"Inside" voices are let loose on the outside, and the main pair of Ed and Kath are not afraid to get physical with each other – letting the violent undertones bubble up juicily, as well as getting right in the face of Adam. Boundaries aren't respected any more than taboos are, and it's neatly choreographed to play with the audience's nerves and so bring forth the most laughter.

Gein's Family Giftshop is a guilty pleasure. It may have changed its players, but the ethos and dynamic is still there – coming from left field, and provoking malicious laughter in even the most saintly.