Hero Status by Kristen Brand

Dave Del Toro used to be a superhero. Now he's retired and happily married—to his former nemesis, Valentina Belmonte, better known as the Black Valentine. The two have settled in sunny Miami and left the past behind them. No more masks, capes or handcuffs. At least, not outside of the bedroom.

But then the famous hero Supersonic turns up dead, and Valentina is arrested for the murder. Dave knows she's innocent, but he has to find the real killer if he wants to prove it. Investigating on his own, dodging the law, he gets tangled in a web of conspiracy that will take more than super-strength to break. If Dave wants to save his wife, he'll have to cross lines no hero ever should....