Alice (Emily Beecham) is a London scientist working in a laboratory creating new plants and, working in particular with Chris (Ben Whishaw) and Bella (Kerry Fox). Separated from her partner Ivan (Sebastian Hülk), she is a single parent who lives with her adolescent son Joe (Kit Connor), who sees his father who lives in the country.
Alice has named her new 'child' – a remarkable plant – after her son and called it Little Joe. Little Joe is a plant which gives off oxytocin, and as such can make people happy. The possibilities for the success of this plant are self-evident, although tests must be carried out to ensure it is safe and doesn't produce unpleasant side effects. She does, though, act against protocol and take one of the plants home for Joe.
Bella is an older member of the laboratory team with a history of mental illness from which she has occasional relapses for which she self-medicates. Bella lives for her dog which comes into contact with Little Joe and which Bella perceives as behaving strangely. So strangely, in fact, that Bella claims the dog has changed to such an extent that she no long recogises it: she has it put down. And what's more, she believes the change was caused by Little Joe, which Alice thinks is absurd.
Until, that is, she starts to look at an article in Nature magazine which makes Bella's theory look slightly less improbable. Furthermore, Bella gives Alice a USB key of unedited examples of the people who the plant was tested on, and they have noticed behavioural changes. Joe too seems to be registering changes – which of course (as Chris reminds her) are normal in an adolescent – but Alice no longer seems to recognise him, and she's becoming certain that Bella is right: there's something sinister about Little Joe.
In spite of initial scepticism, the boss Karl (David Wilmot) is convinced that it is safe to show Little Joe to the public. Alice tries to sabotage her own creation but Chris violently stops her, and the result is that Little Joe is such a success that countries all over the world want to buy it, even, says the Irish-accented Karl – and no doubt with a critical wink from Austrian co-screenwriter Hausner – from EU countries!
An intelligent film, rather surprisingly in the thriller genre.