A troubled young woman offers to act as a surrogate for a well-off couple in an engrossing new drama which explores moral issues – and maybe even darker themes

Well, now, here’s a pretty to-do. Thirtysomething Emily (Sophie Rundle) bumps – literally, with her car – into an 18-year-old girl arguing with a man in the street and offers her vehicular sanctuary from her apparent aggressor and a lift to the hospital. The girl, Kaya (brilliant newcomer Mirren Mack), accepts the offer but gets out of the car early to head home instead. By rights, they will never see each other again. But the fates (and the scriptwriter) have other ideas.

So begins The Nest, BBC One’s knotty, moreish new thriller , the five parts of which you can safely add to your stockpile of distractions. It is based round the central question of how far people will go to get what they want – in this case, a child. Emily and her husband, Dan (Martin Compston, whose relative absence from our screens since he first broke through in Line of Duty has always been a puzzle) have almost reached the end of the line in their attempts to get pregnant. After a series of IVF procedures and miscarriages, Dan’s older sister, Hilary – a nurse – agreed to act as a surrogate. While treating Kaya when she returns with complications from the car accident, Hilary starts to miscarry. Kaya recognises Emily and Dan when they arrive and overhears enough to know that Hilary has lost the baby and gain an understanding of the couple’s situation. She offers to help.

What would you do? If, like Emily, you had one frozen embryo left for implantation? If there was a young, willing womb for hire in front of you?

The Nest does a nice job of thickening the plot with wider questions about the morality of “buying a baby” and exploiting the vulnerabilities of others without letting it hold up the plot or dissipate suspense. Dan is a self-made man and the couple enjoy every material comfort and they are happy together. Should this be enough? Dan could manage without a baby. Emily says she cannot. Is that self-indulgence, or is baby hunger a quite different kind of appetite from all the ones we try to limit and control?

Much of the suspense, especially before the last few scenes, which suddenly immerse us in a variety of new expectations and possibilities, comes from trying to work out just how vulnerable Kaya is. We are given to understand that she has just come out of care – the man she was arguing with is her keyworker James. Does this make her too damaged to know her own mind – Dan’s refusal to adopt a child is based on the assumption that anyone they take will have already been irreparably harmed in some way – or be capable of altruism?

She says she wants to do a good thing, but also to charge the going rate for surrogacy in countries where paying for the service – rather than, as in the UK, just the surrogate’s “expenses” – is legal. So, £50,000 instead of about £15,000. It is money that, in her view, will allow her to start a business, be independent and firmly uncouple herself from the life she has known. “Get involved with normal folk,” as she puts it. “Not filthy charities and housing associations.” Should a society that has deprived her of so much also curb the use of what has unexpectedly become a major asset – her fertility? But what are we to make of her stated desire to be on the receiving end of gratitude for once, instead of its everlasting giver? And how much does helping one individual harm us collectively by normalising the commodification of children? Do we live in a world where foolproof safeguards for women and their reproductive rights and capacities exist?

Fascinating series to watch for sure.