03:17 A.M.

The moment the first rift appeared. After it, a run of overwrites and rifts locked again and again onto that stretch of time a little past three in the morning, tightening down further and further between the minutes and the seconds.

The opening in the brick wall existed from 03:15:40 to 03:18:20, 161 seconds. The window for that passage under Ximen Station was 03:11:15 to 03:18:30, 435 seconds. The two cases differ in medium, in scale and in method of observation, and the durations can't be set directly against each other as larger and smaller; what does line up is the moment of withdrawal — between 03:18 and 03:19, both cut back to their original versions.

The moment of the switch can be heard as well as seen. The platform's air-conditioning, the announcements and the hum of the light boxes drop together to something close to background, as though someone had pushed the volume knob down; the colour temperature of the lights turns slowly from cold white towards yellow, and the next station on the screen flips into two block characters.

The points inside this stretch of time line up one against another as well. The full span of the first night was 03:11 to 04:33: the time-sync photo of the street corner on Songshou Road at 03:09, the first look upward noted at 03:14, the line seen at 03:17, the convenience store 70 metres away entered at 03:19. Deep in the opening in the brick wall, the yellow light came on at 03:16:08. On the underground platform, the nearest carriage door was hauled sideways open from inside the carriage at 03:17:08.

03:00 to 04:00 in the small hours is this city's most dangerous hour. Inside a rift zone, in that stretch of time, the rules of reality loosen; what happens leaves no evidence, and afterwards nobody remembers.

This time slot has another use. Six Bannan Line disappearances filtered out of the police's public missing-person notices all entered stations between 02:00 and 04:00 in the small hours, and none of the 6 has an exit record for that day. In a batch of old case files taped shut and left for twenty-odd years, the last-seen times on the handwritten cards mostly read 03:14, 03:17, 03:18.

After 04:00 everything looks normal again — normal enough to look as though nothing had happened at all.