Our Mother's House by Julian Gloag
"Mother died at 8:58" So begins this story of seven extraordinary children who, faced with the unknown terrors of an orphanage, decide not to report their mother's death. They bury her in the garden, telling people only that she's too sick to have visitors. Then a menacing stranger appears, claiming to be their father. He agrees to keep their secret-and from that moment the story moves relentlessly to its mesmerizing climax.