In the office of the Manhattan Property Clerk, evidence and lost items arrive by the tens of thousands. A small band of officers and civilians has to manage never-ending pressure.

Charmain Carryl moved with purpose through the dim, cavernous room.

She turned down a shadowy aisle of rolling library stacks and scanned the shelves until her eyes landed on the aim of her pursuit: a samurai sword.

The sheathed blade, an identification tag tied to its golden hilt, is just one oddity kept in the basement of New York Police Department headquarters.

The office of the Manhattan Property Clerk, as it is known, is a subterranean repository for lost objects and the tangible aftermath of crime and misadventure. Ms. Carryl has been a police evidence and property specialist there for more than a decade. Thousands of people walk through One Police Plaza each day not knowing an archive that allows the criminal justice system to run is just one story below their feet.

Almost every item that passes through the borough’s 22 precincts must go to the basement to be numbered and cataloged to be held as evidence for a trial or wait for its rightful owner. Some objects come from crime scenes. Others were turned in after they were left behind on a park bench or a sidewalk.

Ms. Carryl supervises the meticulous bookkeeping. She keeps track of the expected — guns, drugs, samples of DNA — and the bizarre: a gold dental grill, a half-drunk bottle of Smirnoff and a weathered brown suitcase. It is stuffed with muskets.