Humans series 2, episode 2 review: are the Synths heading for all-out war?

The big question casting a shadow over Humans is simple: will the rise of artificial intelligence lead to a brave new world... or all-out war?

With violence and mistrust brewing, this latest episode presents many of the show's characters at a crossroads, with their next move having the potential to tip the scales one way or the other.

Hester (Sonya Cassidy) is a product of historic abuse and recent persecution, but her decision to take a man's life is certain to have serious consequences. It couldn't come at a worst time for Synths, either – what with Niska (Emily Berrington) already facing down an unsympathetic judicial system.

If you're still holding out hope that Synths and humans might peacefully co-exist, these are not good signs – and neither is the swift disintegration of Mia's relationship with Ed (Sam Palladio).

It was inevitable that Mia's growing feelings for the struggling café owner would end up exposing her – and Gemma Chan is superb at expressing so much whilst doing so little – but Ed's bad reaction to the truth hints that perhaps Leo's right when he warns against making attachments.

Then again, Leo (Colin Morgan) is facing a moral crisis of his own: as part-man, part-machine, could he overcome his fear and cynicism and be the one who brings humans and Synths togther?

With Laura (Katherine Parkinson) fighting for Synth rights and Mattie (Lucy Carless) quite literally saving Odi (Will Tudor) from the scrapheap, it's just as possible that it'll be the Hawkins family who are the deciding factor in all this.

Keep an eye on Joe (Tom Goodman-Hill) though; he might be playing The Good Husband right now, but with a Synth taking his job and Laura's crusading certain to take her away from home, will it stick or will his feelings of inadequacy and resentment rear up again?

The next step for Dr. Athena Morrow (Carrie-Anne Moss) and Milo Khoury (Marshall Allman) over in San Francisco is even less certain. On paper, there should be very little that's sympathetic about Morrow – a ruthless scientist hacking Synths to bits for her own ends – but Moss's terrific, world-weary take on the character relates so much about how she's been driven to this point.

Allman's slippery billionaire meanwhile has something in store for the Synths – and perhaps more so than any other character in this series, it's tough to predict whether he'll land on the side of the angels or end up a significant threat.

Humans continues to be enjoyably unpredictable: two weeks into this second series and there's still a whole heap of possibilities as to where the story could go. As Laura tells Niska, "This is uncharted territory – there are no guarantees."

One thing that's consistent, though, is how the series continues to deal in big social themes – civil rights, man's inhumanity to man, even teenage isolation – with a sci-fi slant, and without ever coming off as preachy or self-righteous.

Much of that is down to some much-needed moments of humour and warmth, which Humans never neglects to include. After all, if you're telling a story about what it means to be human, surely these qualities are the most important?