WATERTOWN, Mass. — For just a few minutes, it seemed like the dragnet that had shut down a metropolitan area of millions while legions of police went house to house looking for the suspected Boston Marathon bomber had failed. Weary officials lifted a daylong order that had kept residents in their homes, saying it was fruitless to keep an entire city locked down. Then one man emerged from his home and noticed blood on the pleasure boat parked in his backyard. He lifted the tarp and found the wounded 19-year-old college student known the world over as Suspect No. 2.

Soon after that, the 24-hour drama that paralyzed a city and transfixed a nation was over.