this time lugovoy brought along a buddy, a man named dimitry kovtun.e in the black turtleneck. it was a quick meeting. litvinenko drank just half a cup of tea then left. around 5:00 p.m., he caught a ride home. that night, he fell ill. and three weeks later, he was dead. so, who so slipped litvinenko poison that day, putting his murder into motion? litvinenko told scotland yard detectives before he died he didn't know when or who had poisoned him. but he had no doubt that one or more of the men he met that day. the two russians or the italian was his killer. naturally, we wanted to talk to all three. >>> coming up we track down the first suspect named. are you frightened for alexander litvenenko, the former russian agent, the man friends called sasha, died without knowing what killed him. the results from a battery of tests came in too late. but they did come in. it turned out he was killed by something far more lethal than common rat poison. >> it's polonium! >> reporter: polonium 210 to be exact, a rare and deadly radioactive isotope. the news shocke