The speaker is looking through photographs taken by someone named Henri, and recognizes a shared longing: both of them want to stop time. The asterisk after the name suggests a note the poet meant to explain who Henri is, but we don't have it here, so we can only read him as a photographer whose pictures the speaker studies.
The poem treats photographs as small rescues. People smile, cry, frown or drift into thought, and for a moment their inner lives show. But the glimpse is quickly "taken away in the flood." Time is pictured as rushing water, faster than any river, carrying life off in swirls until nothing is left. The ending is stark: a person is reduced to a dash between two years.
The mood is wistful and quietly sad, with a note of desperation. The short, final lines feel like a breath running out, leaving the reader with how little space a life takes up.