A Canadian man accused of plotting a terrorist attack on New York is being held in custody overseas, an FBI source knowledgeable about the investigation said Friday. This suspect is one of eight people — three of them in custody — who, investigators say, were planning to bomb heavily used commuter tunnels leading to Manhattan with the aim of flooding the financial district at the south end of the island. A version of the alleged plot was revealed Friday morning in a New York daily newspaper, prompting the Federal Bureau of Investigation and the Department of Homeland Security to hold...