Lion & Lamb by James Patterson & Duane Swierczynski

They can catch a killer—if they don’t kill each other first. Veena Lion and Cooper Lamb are rival PIs working the same intense headline-making case.  Philadelphia is in a state of shock over the fate of two hometown Eagles starting quarterback Archie Hughes, and his even more famous wife, Grammy-winning singer Francine Hughes.
 
One spouse is murdered. The other is suspect #1.
 
Even before the case hits the courtroom, it’s the hottest ticket in town. 
 
For the Cooper Lamb, private investigator to the stars.
 
For the Veena Lion, a sleuth so bright she’s got to wear shades.
 
Between them, they know every secret in Philadelphia. Together, they prove how two wrongs can make a right. They are Lion & Lamb.