The Spying Game

Even at the best of times, Northern Ireland's peace process resembles a roller-coaster ride. But the lurch it took last week was so unexpected that many riders may be thrown off the track.

On Friday, police showed up at Stormont, the seat of Ulster's government, and went straight to the offices of Sinn Fein, a key partner in the province's power-sharing arrangements. Detectives seized computer discs that, police said, might contain evidence that the Irish Republican Army spied on the British government during the peace process. The raid was the tail end of a major police operation in...