If Death Ever Slept

the long version

Published 1957. Millionaire Otis Jarrell retains Nero Wolfe to get sufficient information on his daughter in law to persuade his son to divorce her. Susan Jarrell is not only unfaithful but she's selling business secrets to one of Jarrell's competitors - or so Jarrell claims. Archie goes undercover as the millionaire's new personal secretary but two murders later, Wolfe has to call in not only his usual trio of PIs but also Sally Colt and Dol Bonner to help with the legwork tracking down a very clever and cold-blooded killer.