The Camera Fiend by E.W. Hornung

In days to come, when the boy had schooled himself not to speak of these days, nor to let his mind dwell on their mystery and terror, it was as a day of dark hours and vivid moments that he remembered the one which Phillida and he began alone together in her uncle's house. Those endless hours were either mercifully forgotten or else contracted to an endurable minimum; but the unforgettable moments would light themselves up in his memory without a detail missing.

There was their first encounter at the dark-room door, and Phillida standing all but barefoot in the ruby light, with her glorious hair about her shoulders, a picture that could never fade. Then there was the moment of the incriminating print, which the sun wiped out even as Phillida stood with it in her hands. That moment merged itself in the greater one of his discovery that the revolver was fully loaded, his inspiration that neither it nor he had done the fatal mischief in the Park. Then she was begging him to go (she who would keep him the time before! ) and he entreating her to come with him, and neither giving way an inch, so that they quarrelled just when they should have stuck together, and she ran away in tears, and he stayed below in a glow of anger which dissolved his fears like snow in May.