Like a mirage, the Sierra Club hikers pooled by the Griffith Park Merry-Go-Round and then rippled quietly away.
By a few beats after 7 p.m. Tuesday, 200 of them had collected their yellow plastic bags and disappeared in small groups onto the trails and back roads of the park.
"When the Sierra Club says 7, it doesn't mean 5 after 7," the leader of the last group, Richard Boothe, said, turning smartly up a small stream-bed trail.
The hike begins that way every Tuesday and Thursday. But the yellow plastic bags were new. The bags, each accompanied by a clear plastic glove, were donated by a fast-food franchise to turn Tuesday's standard Sierra Club hike into a spontaneous trash pickup.
Only about a third of the hikers in Boothe's group carried bags.
"It's teamwork," one stout young man explained, sidling up to his companion. "I've got the bag and she's got the glove."
The trash duty proved no hindrance.
In fact, there was so little trash that some of the hikers squeezed their bags into little balls and others let them open to the air like balloons.
A small cheer went up from the group every time someone found a beer bottle, a plastic cup or a Twinkie wrapper.
"It's not too bad right here on this trail," Boothe conceded. "But there are some roads that are just appalling."
Even so, by a quarter to 8, when Boothe stopped at a trail junction called Five-Points, he and a couple of others had filled their bags almost half full.
After only a brief rest, the group moved on into a mountain sunset. At the end of the hike, they would deposit their bags on the road for the Griffith Park Rangers to pick up.
And today, even if it wasn't that dirty to begin with, Griffith Park is cleaner still.