The major conflict in Wait Till Helen Comes is how to make a little girl with a bad disposition and a seriously horrific tragedy behind her feel loved, wanted and cherished, especially when she doesn't behave in a way conducive to generating feelings of love, desire and adoration in other people, which is all compounded by the fact that adults are making decisions that are good for themselves but not necessarily good for her. The mother of Molly and Michael marries Dave, the father of Heather who is younger than either Molly of Michael. They marry because she paints and he pots (makes pottery, that is). Heather has been through a terrible ordeal relating to her mother's tragic death. The adults hope the union of the two families will help restore Heather to a sense of well-being and belonging.
Everyone in the family, including generously-hearted Dave, is on the self-absorbed side, so Heather doesn't find the welcoming unity that the adults hope will envelop her. One of the things that the new family does is to buy a disused church in the woods of Maryland with a great place for potting and another great place for painting. Molly and Michael are told they simply have to give up their long cherished plans for a writing Enrichment Program and a summer science program and get used to exploring woods. Heather uncommittedly accepts what she is handed. In the woods Heather finds someone who promises to never leave her and to always cherish her. Unfortunately, the someone is a less than friendly ghost who desires Heather for her own purposes. The inclusion of Helen the ghost demonstrates just how far heather will feel driven to go in her quest for despair-free belonging and love.