Yes, it's not remotely credible but The Drowning is a no-nonsense thriller that keeps you guessing

Rupert Penry-Jones and Jill Halfpenny star in The Drowning - Channel 5
Rupert Penry-Jones and Jill Halfpenny star in The Drowning - Channel 5

The Drowning (Channel 5) is one of those snappy thrillers that will keep you watching right to the end, provided you suspend disbelief and refrain from yelling: “What on earth are you doing?” and, “Why haven’t you done these very obvious things that a normal person would do in this situation?”

It operates in its own dramatic universe, one in which the police have closed the case on Tom, a young boy who disappeared during a family day out by the lake, concluding that he drowned even though his body was never found. His grieving mother, Jodie (Jill Halfpenny), is driving to an appointment nine years later when she spots a boy on his way to school who bears an uncanny resemblance to her son: right age, same hair, and – surely the clincher – a matching scar beneath his left eye.

Jodie starts off by doing the things we’d probably all do – rushes off to tell Tom’s father, goes to the police and asks them to investigate. But when both treat her as if she’s losing her mind, she decides to conduct her own investigation and gets a job at the boy’s school. This is where we need to skim over issues of credibility, such as Jodie’s behaviour not raising any alarm bells with the head when she turns up to work before she’s officially got the job, puts up posters for a lunchtime music group then conducts a lesson, all without being on the staff list.

Why didn’t Jodie take a picture of the boy when she followed him on the bus (she had her mobile phone in her hand because she used it to pay her fare)? Why hasn’t she done the old TV drama trick of taking a hair from his head and sending it off for DNA analysis? (Perhaps a later episode will reveal that he’s adopted.) Why hasn’t she mentioned any of this to her close friend and business partner? Can she actually play the guitar?

Never mind all that, because here’s Rupert Penry-Jones as Tom’s, sorry, Daniel’s, father, Mark. He lives in a fancy house – a bit like the one in Finding Alice, but hopefully adhering more closely to building regulations. Unlike Finding Alice, which is still limping along on ITV, there are no attempts to chuck in different genres. It’s a no-nonsense thriller, competently acted by its leads to keep us guessing: Halfpenny plays Jodie as a woman who could equally be deluded by grief or bang on the money; Penry-Jones’s character is inscrutable.

Of course, it could all go downhill from here and give us an unsatisfying, cop-out of an ending. But on current form it’s highly watchable, and stripped over the next three nights.