My Gal Sunday by Mary Higgins Clark was originally published in 1996.
Mary Higgins Clark - My Gal Sunday book description:
A dashing ex-president and his young congresswoman bride become an irresistible sleuthing duo in four acclaimed stories from the Queen of Suspense.
Henry Parker Britland IV - wealthy, worldly, and popular - is enjoying an early retirement. His new wife, Sunday - as clever as she is lovely - has just been elected to Congress in a stunning upset victory that has made her a media darling. Henry and Sunday make a formidable team...and never more so than when they set out to solve baffling high-society crimes.
From a long-unsolved case they reconstruct aboard the presidential yacht to a kidnapping that brings Henry frantically back to the White House, the former president and his bride engage in some of the most audacious and original sleuthing ever imagined.