The quote in question appears in stave 1 and is found on page 18 of my edition. The quote comes just as Scrooge sees Jacob Marley's ghost come up the stairs and enter the room that Scrooge is sitting in. Scrooge is a miserly fellow, so his house is not well lit. He uses as few candles as possible, and the fire that he is currently keeping is as low and miserly as Scrooge himself. When Jacob Marley's ghost enters the room, readers are told that the dying flame of the fire or candle leaped up as if it were crying out that it recognized the ghost as Jacob Marley. The flame then falls back to its normal, low state.

The leaping flame is a nice image that further highlights how Scrooge probably initially reacted upon seeing the ghost. Scrooge is momentarily shocked by the sight of the ghost. There is probably a wonderful mixture of fear, surprise, and excitement. Medically speaking, Scrooge probably got a nice dose of adrenaline as his body prepared for fight or flight; however, Scrooge is a tough old guy. His surprise is momentary, and his heightened emotions are quickly quelled in the same way that the flame died down. Scrooge returns to his normally cold self just like his fire returned to a state of barely throwing enough warmth for his body.

he was still incredulous, and fought against his senses.
“How now!” said Scrooge, caustic and cold as ever. “What do you want with me?”