Thrown to the Lyon by Jude Knight

When Dorcas Anderson saves Mrs. Dove-Lyon from being crushed by a passing dray it sets up a chain a series of events she could not have imagined. The grateful lady insists on presenting to her rescuer a tinder box containing three tokens. Each can be exchanged for a favor from The Black Widow of Whitehall herself.
She needs the first sooner than she expected, when her dead husband’s twin, brother to a powerful duke, has her and her four-year-old son arrested for theft.
When Mrs. Dove-Lyon asks him to help rescue a wrongfully arrested widow, Ben, the Earl of Somerford, is glad to aid Mrs. Anderson, whom he knew and respected when he was with the army in the Peninsula.

Dorcas uses the second token to enlist Mrs. Dove-Lyon in catching Ben’s attention, little knowing that Ben is already wondering if Dorcas is just the wife he needs.