Two lovers picnicking in a field north of London are stunned when an out-of-control hot air balloon comes scudding past, a young boy trapped in the basket. The man (Daniel Craig) races to the rescue along with three other bystanders, but heavy winds pull the balloon aloft and one of the rescuers is killed. It's a powerful opening, and the emotional repercussions of such a split-second tragedy promise a rich and thoughtful drama. But the story, taken from a novel by Ian McEwan, veers off course when the man, a steely academic, finds himself stalked by one of the other rescuers, a ratty bohemian (Rhys Ifans). Director Roger Michell (Changing Lanes, Notting Hill) seems genuinely taken with the contrast between brotherly love and homosexual obsession, but these themes are overwhelmed by the suspense machinery. With Samantha Morton and Bill Nighy. R, 91 min.