Teenager Zach and his mum, Helen, are not getting on. He’s preparing for his future while she may not have one. Will physicist Bob Bliss heal their rift, or does he have another motive for dropping into their lives?

It’s something of a signature for this series that we begin the tale somewhat innocuously before discovering we’re watching an entirely different genre. This week is a prime example. We begin with a rather familiar scenario – the mutual frustration between a stressed single mother and her disrespectful teenage son. He doesn’t quite reach “Kevin the Teenager” levels of “ugh, I hate you” but he’s not far off. You’ll probably want to give him a stern talking to, especially as his mum (Jessica Hynes – W1A/Spaced) obviously loves him but has her own worries, especially today.

Steve Pemberton’s Bob Bliss soon turns up with an injured bird that just hit Zach’s window, which leads to the act of kindness of the title. With his peculiar verbal tic and knowledge of science there’s clearly some sort of unknown connection between him and this family, and Helen seems to take to him almost immediately. It’s a good while before the nature of this character becomes clear, and when it does is when we realize we’ve been watching something else entirely.

The back end of this episode I can’t even touch here, except to say it sheds light on Reece Shearsmith’s Open University-style drop-ins that have peppered this instalment. I will say that you do need to pay attention, this is an episode that asks you to do some of the work too.

Performance-wise Pemberton is as good here as he’s ever been and Noah Valentine as moody Zach hits the right hormone-fuelled notes. Hynes though is the standout, I’ve enjoyed her work ever since Spaced finally showed how to do flatshare sitcoms right and she doesn’t disappoint. It’s her character that the story really revolves around, she just doesn’t know it, and plays it as if she were in a fairly straight light drama instead of something that’s actually quite mad.

Verdict: A bit of a head-scratcher that begs for a repeat viewing; there are sure to be plenty of “yes of course!” moments the second time around. A pleasure to watch, with more than a whiff of Ray Bradbury about it. 8/10

Andy Smith