Martin's newest gizmo, a molecular reassembler, switches the psyche of the two subjects to which they are exposed. Martin would like to use it to eliminate all hostility in the world, not to switch his and Mrs. Brown's psyches, which is what happens, just before Mrs. Brown is ready to go out on a date with Det. Brennan. Martin, looking like Mrs. Brown, is especially not looking forward to a date with Det. Brennan, but needs to do so not to attract the detective's suspicion. Martin is even more perturbed that the detective wants to ask Mrs. Brown to marry him. But of utmost importance, Martin needs to change himself and Mrs. Brown back within a couple of hours, or this switch will be permanent. Unfortunately, Martin has run out of the mineral needed to exact the change. Fortunately, Martin thinks that a diamond, which has a similar make-up, will work. The mixed blessing is that neither "Mrs. Brown" or Tim have a diamond, however Det. Brennan, ready to propose, has a diamond ring in his possession. Martin, as Mrs. Brown, gets the detective to propose just in time to get the ring and change himself and Mrs. Brown back. However, after the change back, Mrs. Brown has no recollection of any of the evening's events, including the proposal. Martin manages to slip the ring back in the detective's pocket, who ultimately thinks he's losing his mind.
—Huggo