Joe and Claire (Craig and Morton) are picnicking near Oxford when a startling event involving a hot air balloon changes the day ... and their life. Back home in London Claire takes it in stride, but Joe's haunted by feelings of guilt and fear. And this gets worse when another man from that day, Jed (Ifans), keeps showing up, dropping hints and insinuations that something else is going on here. It takes Joe awhile to realise he's being stalked by a madman. But Claire thinks Joe's the one who's lost the plot.

This is such a delicate story, intricately balancing its characters on a knife-edge of compassion and obsession, while they examine their lives with an intensity that's almost overpowering. Fortunately, Craig, Ifans and Morton are more than up to the challenge--their performances are astonishingly raw and affecting, digging deeply into the hearts and minds of their characters while prodding our own thoughts and emotions.

Penhall's script opens up the story slightly, adding some superfluous new characters (such as friends Nighy and Lynch) and building an awkward, slow-building tension between Joe and Jed. All of the relationships in this film are strained by that initial shocking event, and the script carefully lets the repercussions ripple outwards through its razor-sharp dialog. But Penhall also gives the characters space to breathe, with moments of meaningfully introspective silence.

Michell orchestrates this beautifully, with a lush-but-gritty look that grabs shapes and colours, echoing events and themes while drawing out Joe's consuming self-doubt with questions about life and death, love, bravery and madness. As it grows steadily creepier we worry that it will turn into a Fatal Attraction-like tale of obsession. But there's something much more subtle going on here that really gets under our skin.