One night

 "One night the power goes out at Halliwell Manor. Piper is looking for candles and finds an old, blue candle with the name “Melinda” engraved on it.

Phoebe jokes, “Maybe it’s a ghost candle… Light it and someone will appear.”

Piper lights it. The flame flickers, never going out — no matter how hard she tries to blow it out, smother it with her hands, and even pour water over it.

That night, Paige dreams of a long-haired girl in a 17th-century dress, whispering,

“Keep the fire burning. When the light is gone, darkness will reign.”

The next morning, they find the Book of Shadows opening to a new page with the words:

“Melinda’s candle only burns when darkness is near.”

The sisters know something is awakening… and the candle is the first warning."