2 Sisters Murder Investigations: A Thriller (A 2 Sisters Detective Agency Mystery: Book 2) by James Patterson & Candace Fox

Patterson’s greatest crime-solving team since the Women’s Murder Club is the Bird Sisters. 

Rhonda and Barbara “Baby” Bird are half-sisters—and full partners in their Los Angeles detective agency. They agree on nothing.
 
Rhonda, a former attorney, takes a by-the-book approach to solving crimes, while teenage Baby relies on her street smarts.  
 
But when they take a controversial case of a loner whose popular wife has gone missing, they’re accused of being PIs who can’t tell a client from a killer. 
  
The Bird sisters share a late father, but not much else…except their willingness to fight.
 
Fight the system. Fight for the underdog. Fight for the truth. If they can stop fighting each other long enough to work together.