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Yang Yi finally made his way to the seventh floor.
The apartment building had twelve floors, with eight apartments per floor, adding up to a total of ninety-six units.
By the time he reached the seventh floor, Yang Yi had inspected the gas in twelve apartments and recorded each inspected household in his notebook, noting those whose homes were empty because no one was there.
At last, he arrived at the first of the eight rooms on the two floors he needed to check.
Yang Yi knocked on the door, then listened carefully for any sounds from inside before knocking again.
After knocking for longer than he had at other places, but still with no one answering the door, Yang Yi moved on to another apartment.
Out of the eight apartments on the seventh and eighth floors that were most likely used for surveillance of Charles, only two were opened—one with an entire family inside, two children and two adults, and another with a woman in her sixties.