The theme in Roald Dahl's short story, The Way Up to Heaven is implication. This work is included in a collection of short stories titled, Kiss Kiss. The stories in that collection deal with the theme of death and have some sort of implication attached to that theme.
In The Way Up to Heaven, it's implied that Mr. Foster knows of his wife's fear of being late yet he seeks to torment her by making her late for everything. However, one can argue that this implication is a creation of Mrs. Foster's own fear of being late and her unhappiness from being so far from her grandchildren.
Later, Mr. Foster finds himself the victim of an accident. It is not said outright that his wife is aware of his accidental death when she decides to leave for Paris, yet it's implied that something is not right. In Paris her whole demeanor changes and she becomes more confident and is happier.
Upon her return home, she enters the dwelling and it's implied that she is satisfied by what she finds at home. The actions she takes once in the house imply that whatever she finds is fine by her and is the result of her own actions. The end of the story finds Mrs. Forest waiting for the repairman to fix the elevator because apparently, it is broken. A noted absence is that of Mr. Forest.