[Update: Con Edison apologized for the power outage, but offered few clues about the root cause.]

A power failure plunged a stretch of the West Side of Manhattan into darkness on Saturday night, trapping people in subway cars and elevators for a time, leaving drivers to fend for themselves at intersections with no traffic signals and eerily dimming the lights in a swath of Times Square.

Stores emptied out, and Broadway shows did not go on: Most theaters canceled their performances. In restaurants and bars, people drank by the glow of their smartphones.

But the lights — and, on a warm Saturday night in midsummer, the air conditioning and fans that keep people cool — began to return about 10 p.m. Power was fully restored by midnight, with cheers ringing out on the streets in response.

Con Edison said that the power failed at 6:47 p.m. and that 73,000 customers were in the dark for at least three hours, mainly on the West Side. The blackout stretched from 72nd Street to the West 40s, and from Fifth Avenue to the Hudson River.