Baines decides that if Diana and Tom are seen to be mentally incompetent it will give him power of attorney over them and end all his troubles, particularly as the home is in financial difficulties. So he refers them to psychiatrist Dr.Darrow, for whom they act out a well-rehearsed pantomine of odd behaviour, leading the doctor to conclude that they are not mad, just a touch eccentric, with unexpected help coming from Sarah. (thetvdb.com)