When one by one, the friends of a young woman living in Beijing began disappearing — detained by the police after attending a vigil together weeks earlier — she felt sure that her time was nearing.

“As I record this video, four of my friends have already been taken away,” the woman, age 26, said, speaking clearly into the camera in a video recording from late December obtained by CNN.

“I entrusted some friends of mine with making this video public after my disappearance. In other words, when you see this video, I have been taken away by the police for a while.”

The woman — a recent graduate who is an editor at a publishing house — is among eight people, mainly young, female professionals in the same extended social circle, that CNN has learned have been quietly detained by authorities in the weeks following a peaceful protest in…