AP Photo

Mary and Rick Todd were anxious about entering the apartment where their oldest son had lived and died. Late last June the couple had flown from Montana to Denver to Los Angeles to a colonial-era house in the Chinatown district of Singapore to try to make sense of an unthinkable loss: Shane Todd, a young engineer who had just wrapped up an 18-month stint with a government research institute known as IME, was dead – an apparent suicide, according to the Singapore police. Mrs Todd felt her heart pounding as she climbed the narrow staircase to his apartment and thought about what the police had told her a day earlier.

Shane had died a week before he was to return to the US. The police said he had drilled holes into his bathroom wall, bolted in a pulley, then slipped a black...