Promise opens with Hajar (Lara Sawalha), a young middle-eastern woman, arriving at the house of Sarah (Rebecca Callard) and Abe (Nabil Elouahabi), a couple seemingly on the rocks. It’s not made explicitly clear what’s happening to start with, but after glimpses of a pregnancy pamphlet, Hajar’s early-morning vomiting and Sarah’s strap-on belly, it’s easy to work out what’s going on.

With Hajar being an illegal immigrant, the couple have to keep her hidden in her house for the whole nine months. This of course sees tensions rise, as Sarah grows jealous of seeing Hajar carrying the baby she can’t, as well as her getting more attention from Abe. Just when it seems obvious what’s going to happen, though, there’s a new, unexpected development in the tale. One that changes the path of the story and makes Sarah have to think about breaking her promise to keep Hajar her safe.

The twist is made all the more striking by the fact that, for the first half of the film, director Neville Pierce and writer Hannah Lee play it as straightforward as possible – though they do drop little hints at what’s to come. Lee is able to tell the story concisely, with dialogue and directions that are low on exposition. Her writing is complimented by Pierce’s use of visuals to tell the story, his style holds the audience’s attention and gives a genuine feel to the film. Together, they turn what could have been a standard melodrama into something more intriguing and tense.

However, while it is well constructed in terms of plot, it hits all its story beats a little too cleanly. Jumping from one plot point to the next does rob the film of its attempt at a natural, realistic rhythm and feel. What’s more, while it presents both the issues of surrogacy and the plight of a refugee well, neither is really probed too deeply and nothing particularly new is brought to either debate.

There’s also some disparity in the balance between Sarah and Hajar’s character arcs – if they are found out, one is facing far worse consequences than the other.

It’s easier to feel more sympathy for Hajar, as her situation is more desperate and dangerous, and Sawalha does well in her performance of a woman who is, at the same time, dealing with being in an unusual situation and environment, the physical and emotional challenges of her pregnancy and the more serious issues that surround it. Her final scene in the film is particularly effecting. The film may want us to feel ambivalent towards Sarah, but by the end, there’s not as much emotional weight to want to get on her side.

The construction, craft and technical ability of Promise is easy to admire while watching it. It’s well-made and thought-provoking, but it won’t keep you thinking about it for long once its over.