For the next several years Heyer published one romance novel and one thriller each year. The romances were far more popular: they usually sold 115,000 copies, while her thrillers sold 16,000 copies. According to her son, Heyer "regarded the writing of mystery stories rather as we would regard tackling a crossword puzzle – an intellectual diversion before the harder tasks of life have to be faced". Heyer's husband was involved in much of her writing. He often read the proofs of her historical romances to catch any errors that she might have missed, and served as a collaborator for her thrillers. He provided the plots of the detective stories, describing the actions of characters "A" and "B". Heyer would then create the characters and the relationships between them and bring the plot points to life. She found it difficult at times to rely on someone else's plots; on at least one occasion, before writing the last chapter of a book, she asked Rougier to explain once again how the murder was really committed.