This is book 6 of the "Mac McRyan" series.

This note contains spoilers for the book.

On vacation in St. Paul, Mac gets drawn into an investigation of some murders, including one that his ex-wife is accused of.

This ends up connecting to events in Washington and in South Dakota—high politics and oil-industry money.

Sally isn't around much, though she is urging him to be careful from a distance (and his police friends are on her side). She does approve his trying to clear his ex-wife; Mac has a big enough chip on his shoulder that clearing it off seems beneficial to her, and this should do it she thinks.

His connections to the serving President do show up a little bit. Seems like thriller writers are converging, since John Sandford, Stuart Woods, and Tom Clancy all do this.