The Replacement series review, BBC's maternity leave thriller ★★★★★

It's amazing that no one has ever thought to write a thriller about this before. There have been plenty of storylines about identity theft – The Net, The Talented Mr. Ripley, Catch Me If You Can. Yet, every year, thousands of women go on maternity leave, placing their working lives into hands of the stranger who covers for them whilst they convalesce.

Enter the BBC. Only a few weeks after the magnificent Apple Tree Yard the Corporation is back with another female-focused thriller. Episode one introduces Ellen (Morven Christie), the rising star in a Glasgow architecture firm. While working on a career-defining project, a library, she finds she is pregnant.

Ellen's practice hires a temporary replacement to fill in for her for a couple of months. Ellen is ambitious. She doesn't want to be out of the game for long. The library project is her other baby – she jokes about 'having twins'.

In episode two, the replacement, Paula (Vicky McCluster), starts to cause trouble. She tampers with Ellen's designs for the library, ingratiates herself with her clients and cuts her out of discussions with the boss. Could it be that Paula aims to hold on to that which is only temporarily hers?

We all recognise office tensions – the power dynamics and gossip, the long, silent struggles for workplace domination. Writer and director Joe Ahearne's clever script eases us into a situation many are familiar with – yet few understand.

Where the first two episodes offered simmering tensions and the occasional outburst, the third episode goes hell for leather as all-out insanity erupts and the two women go for each other's throats. An excellent series is almost ruined by the ludicrousness of the finale, which is a pity.

Nevertheless, The Replacement rewards watching, a timely study of women in the workplace that poses, among other questions, a fundamental one – career or family? Thank goodness someone has at last addressed that in a television drama.

The Replacement is on BBC One at 9pm on Tuesdays. Catch up on BBC iPlayer.

Helena Kealey