Doctor Foster episode four review: thrilling show sets up a deadly climax in Suranne Jones drama

Still, while her continued failure to tear him limb from limb in favour of yet more plotting and conniving continues to strain credulity, tonight’s instalment set up a potentially very satisfying finale.

But it took a while to get there. There was a brief interlude when everything seemed to go wrong at work (Gemma is suspended, her various breaches of professional ethics finally coming back to haunt her).

All seemed to be well on the marriage front before she saw Simon (Bertie Carvel) and Kate (Jodie Comer) in the garden of his workplace kissing and cuddling; this prompted yet another moment of agonised misery from Suranne Jones who must have cried at least three buckets of tears so far this series.

But, instead of making merry hell, Gemma sped off to the coast, to gather her thoughts, contemplate suicide, actually attempt suicide (by drowning) and then finally decide she wanted to live. Good for her, we cheered.

The coastal scenes were probably the best thing about tonight’s episode. It looked stunning for one thing. But it was a relief to just get out of bloody Parminster with all its smug middle-aged people copping off with each other or being (and Polestar in this particular constellation is the ghastly Ros) unbearably self-righteous.

This break helped us understand Gemma’s character a little better. Her parents, we learned, were both killed in a car accident when she was young. No wonder she wants to hold on to whatever scrap of family life she has.

So Gemma has another plan up her sleeve and it unfolded in an excruciatingly awkward couple of scenes at the end.

We left her and Simon round at the Parkes’ rather flash house enjoying dinner with Kate, her parents (who know nothing). And of course Gemma who knows everything. The look on Simon’s agonized face was a joy to behold.

Revenge really is a dish served cold, it seems. But what in God’s name does she have in store for them?