Lucy could hear the heartbeat of the house at night. It woke her, sometimes, with its steady thumping like a drumbeat in the dark. She cried the first few times and was consoled and cuddled alternately by Harold and Julie. As she grew older it became just part of the house and ceased to disturb her or if it did, ceased to frighten. Eventually she found it comforting and missed it during the daylight hours.
Daylight was when her long-dead mother Gillian slept in her coffin in the mausoleum. Only at night could the vampire could watch over her daughter.