At Andy Kenesaw's 90th birthday party, an attempt is made on his life, just before a stockholders' meeting of the company he founded with Mac's grandfather years before (Kenemac Alfalfa Corporation, est. 1901) is held to consider a merger bid from Harvest Foods Incorporated.

Commissioner McMillan celebrates an old friend's wedding, but the honeymoon ends when the bride is murdered, and the intended victim may be closer to home.

Unusual interest is shown in the McMillans' house when Sally thinks of selling it. Then an earthquake reveals a body behind the brickwork.

Mac is wounded in a failed drug raid and sent to the hospital, where he sees a patient smothered, and slowly unravels the case.

Mildred and Agatha are named in a will. Heirs start dying, and next to inherit is Agatha, whose investigation runs parallel to McMillan's.

A naval lieutenant facing a court-martial on a murder charge is appointed counsel in the person of Commander McMillan, USNR.