Color of Darkness — Ruth J. Hartman

Lydia Sullyard is not insane. Truly she's not. To her horror, she's trapped inside Bedlam Hospital against her will. There's only one way for her to gain her freedom, but the consequences are unthinkable. Stratford Bexley agrees to visit Lydia in Bedlam. But the thought of stepping into London's cesspool makes him want to change his mind. And what it will take for her to be released would alter Stratford's life forever. Is Lydia's love strong enough to rescue Stratford from certain ruin, or will he save her life instead?