Darkness Falls

This is a story written by Maple and it's about my fanon Clan called BeachClan. Can you guess sort of what it's all about? Hint hint: look at the title.
Prologue
Night had fallen upon the land beneath the stars, and most things were sleeping. Yet four cats with pelts hidden by the shadows the moonlight cast slunk silently into a clearing.
A she-cat, smaller than the other three cats, had a silver-gray pelt and blue eyes. She spoke in a silvery voice. "This way, Rosethorn."
The other she-cat, a pinkish-orange tabby pelted one, had worried green eyes. Her name was Rosethorn, and she silently wished that the former leader Evergreenstar had not lost his last life. She was nervous.
"Oakstripe, Yowlpaw, you two guard the entrance to the Star Tree," Rosethorn ordered. The two toms, a brown tabby and a blackish-gray pelted one, who were Oakstripe and his apprentice, Yowlpaw, went to each side of a bush.
Rosethorn and the silver-gray she-cat trooped through the bush and into a hidden clearing. Part of it was even darker, because it was shaded by an overhanging cliff. Strangely, there was a tall tree going through the cliff, and it cast a silver glow a fox-length in every direction from the trunk.