How well do you know your partner? My missus is a teacher in a primary school in Wembley, London. Well, she says she is – I have never actually been to it. Recently, she has been spending more and more time there. Planning, she says, marking; she blames the curriculum and the government. OK, but staying overnight? Being away for weeks at a time? Missing last Christmas? Is that normal? I’m probably just being paranoid.

Strangers stars John Simm as Jonah Mulray, whose wife, Megan (Dervla Kirwan), spends half her life in Hong Kong. Well, spent. In the opening sequence, we see her there, driving a car, talking on a hands-free phone, leaving a message for someone. She has got herself into something … she is not sure if she’ll see them again … she wished things had been different.

It sounds serious. Suddenly it is serious, deadly serious, because her car is broadsided by a big yellow truck and Megan is killed.

A lecture Jonah is giving has to be interrupted for him to receive the news, from a policeman who should probably redo the Delivering Bad News training module. Now Jonah is going to have to overcome his fear of flying to go to Hong Kong to identify and bring back the body of his wife. I see: that is why he has not been there before. I cannot use that excuse – a Valium might help the Jubilee line experience, but I am not actually frightened of riding the tube. I am going to follow her to Wembley, next time she comes home.

Anyway, with Mother’s Little Helper, Jonah makes it, rather woozily, to Hong Kong, where at the British consulate he meets a posh lady, played by Emilia Fox. And he meets some stereotypically impassive Chinese policemen. He sees Megan, bruised and laid out cold on a slab. Yup, that is her.

Then he meets Megan’s other husband. Awkward! David Chen (Anthony Wong) says he has been married to Megan for 20 years, 17 more than Jonah. They have a daughter, a rebellious tearaway called Lau (Katie Leung) who has been throwing pink paint bombs at the black car of a property developer she – and a lot of other Hong Kong students – do not approve of.

Poor Jonah. That is an awful lot to hit him in not very much time. One minute he is a happy prof, well liked by his students, in spite of the bad jokes his tells them, and loved by his wife, even if she is away a lot. The next, she is gone for ever, dead; he has got to do the thing he really does not like doing, get on a plane, to a strange place where he does not know anyone; and then he finds out he was not even her only husband. No wonder he is looking a bit frazzled. Simm is very good at being up against it. Strangers might not be the most thoughtful or nuanced of thrillers, but Simm is, as ever, very watchable.

Oh, and his phone is dead and he has forgotten to bring the charger. In fact it must have been out of power, or not switched on, for ages. Because it turns out that the message we saw Megan leaving at the beginning, her last message, was for Jonah. But it means he did not look at his phone in the time it took for the Hong Kong police to find out who she was and tell the British consulate, who told the British police, who tracked him down and sent PC Sensitive round. And then he still did not look at it in the time it took to get a flight to Hong Kong … really? I am not sure Strangers stands up to too much scrutiny.

Jonah eventually gets a (pink) charger in Chungking Mansions in Kowloon. And his message, just the one. Which he listens to. She has got herself into something … she is not sure if she will see him again … she wishes things had been different … she loves him (well, that might be some sort of consolation, I guess).

And then he listens to the crash, the yellow truck, remember? He hears, via voicemail, his wife’s death, and the car rolling down the bank … Hang on, though – she is breathing, she is not dead! But then there is a gunshot. She is now. Two deaths, one for each husband, perhaps. And it is certainly intriguing – maybe even enough to tune in next week.