Murder At Locker 02-069

Susan Taylor Martin, Feb. 11, 2001: He lives alone in the big city.

Weekday mornings, between 9 and 9:30, he steps out of Apt. 3A and rides the elevator down to the lobby. Walks across the black marble floor, buffed to a gleam. Nods to the doorman.

"Good morning, sir," the doorman says.

He is tall and thin, looks to be in his late 30s. Though he has lived here for more than two years, the doorman doesn't know much about him. Just that he's a good tipper, never asks for anything, has few if any visitors.

"Heard he's in the computer field," the doorman says.

As the man ventures out, he slips on dark glasses and moves so softly he's almost tiptoeing. The doorman has never seen him get in a car,…