Upstairs neighbour

The person in the flat above me walks around all night. Heavy, slow footsteps, back and forth, from about 1 in the morning until it starts to get light.

I complained to the landlord three times. He kept saying he'd look into it.

Last week I went up to knock on their door myself.

The stairs end at my floor. I'm on the top floor. I always have been. There's nothing above me but the roof, and the roof is flat, and I've just been up there to check.

There are footprints in the gravel. They go back and forth, back and forth, right above my bed.