Of the many fine touches in Insomnia, Norwegian director Erik Skjoldbjaerg's accomplished and frequently ingenious debut, perhaps the most impressive is how much tension it builds using very little action. It's that rare psychological thriller that actually spends most of its time rattling around the human psyche. What begins as a typical serial-killer movie, centered on the murder of teenage girls by a brilliantly methodical deviant, becomes a penetrating look into the guilt, corruption, and pathology that haunt the lead detective. Stellan Skarsgård (Breaking The Waves, Good Will Hunting) brings a poker-faced intensity to the role of a Swedish cop brought in to investigate the violent death of a 17-year-old Oslo student. During a stakeout, Skarsgård accidentally shoots his own partner (Sverre Anker Ousdal), and, in his attempt to cover it up, he takes an escalating series of missteps that eventually make the case itself seem incidental. Set in the constant daylight of Arctic summer, Insomnia has been aptly described as "sunlit noir." It's a feature of the noir genre that darkness conceals the mind's secrets, but robbed of that simple relief, Skarsgård gradually becomes uncoiled and exposed for who he really is, a conceit that's used to subtle and unnerving effect. In Skjoldbjaerg's world, not even sleep can provide temporary refuge from a guilty conscience.