Detection has occurred. Detonate immediately!  Repeat, detonate immediately

The next time I drew the image up onto the screen the strange mushroom thing was no longer there. Just the trees of the arboretum. I hadn't edited the photograph, I felt sure, and no-one else had used the computer.

Feeling disturbed, I went out for a long walk, down by the river where the scent of the Himalayan balsam is sweetly pungent, and I saw that nature…