Set in suburban London, "Humans" takes place in a parallel present where the latest must-have gadget for any busy family is a Synth - a highly developed, artificially intelligent servant eerily similar to its living counterpart.

TODAY - In Nagasaki, Japan, a hotel staffed primarily by robots will be opening this summer. These robots won't just clean your room and pick up your laundry. They'll check you in, make your dinner reservations, mimic human behaviors and speak four languages. TOMORROW - Your Saturday afternoon errands could result in purchasing a fully functional robotic domestic helper that will get your kids ready for school or take care of an ailing parent. Whether that's a good or bad decision is the question "Humans" sets out to explore. It's not about what this technology is capable of; it's about the impact that this advanced technology will have on the human population. Will this new way of navigating life be detrimental or beneficial to us as a human race? And who will we become when this technology arrives?

At the center of the four concurrent storylines explored throughout "Humans" is the flawed but loving Hawkins family. Joe Hawkins (Tom Goodman-Hill) makes the decision to invest in the latest must-have gadget for any busy family - a Synth. His relationship with his wife Laura (Katherine Parkinson) is becoming increasingly strained and he believes that the addition of a robotic servant to the household will give them back the time they so desperately need and help them re-connect both as a couple and as a family. The Hawkins' new Synth, Anita (Gemma Chan), is an immediate hit, and their chaotic house is suddenly transformed into an oasis of tidy, organized, well-fed contentment. With hesitation, Laura gives in to the family demand, but soon senses there's something different about Anita. There's something not right.

Others, though, have long since abandoned any scepticism and are embracing their Synths as family members. Widower George Millican (William Hurt) has formed a close relationship with his out-of-date Synth, Odi (Will Tudor), whom he treats more like a son than a piece of machinery. When Odi begins to malfunction, the National Health Service forcefully upgrades him with a new stern elder-care model named Vera (Rebecca Front) and George must hide the bond he has with Odi or risk forfeiting him to the authorities.

Meanwhile, a young man named Leo (Colin Morgan) and his Synth, Max (Ivanno Jeremiah), are desperately searching for someone from Leo's past. But who is it, and why? And why does Max seem to be so unlike other Synths? On their heels is a mysterious man named Hobb (Danny Webb), who is determined to uncover a secret before it can destroy humanity as we know it.

Finally, D.S. Peter Drummond (Neil Maskell) works for the Special Technologies Task Force, solving Synth-related disputes to get away from his frustration over his wife's flawless Synthetic physical therapist. Pete spends most of his days pushing papers and solving petty incidents, as Synths rarely, if ever, malfunction, until one day he investigates a case that defies all possibility.

Several months on from the events of series one, Niska (Berrington) is still at large and in possession of the consciousness code. Her synth family, Mia (Chan), Leo (Morgan) and Max (Jeremiah), unaware of her location, are each trying to find their place in the world while Joe (Goodman-Hill) and Laura (Parkinson) attempt to mend their marriage.

As unconfirmed reports of synths behaving inexplicably surface, the ripple effects of one simple yet seismic decision sees the past return dramatically and surprisingly to the door of the Hawkins house. Joe, Laura and the entire family are faced with a difficult choice that will put the family under an intense spotlight.

In the US, Milo Khoury (Marshall Allman), a young Silicon Valley billionaire, founder and CEO of a leading technology company is pioneering new research. But he needs help and attempts to recruit Dr Athena Morrow (Carrie-Anne Moss) - the country's pre-eminent Artificial Intelligence expert. Suspicious of his motives and focussed on her own work Morrow is single-minded in her drive to create a new kind of machine consciousness.

As an emerging form of intelligent life -- the synths -- and an established one -- humanity -- fight for their places in the world, a thrilling multi-stranded narrative evolves which continues to ask: who has the right to determine what it means to be alive?