Who is Catherine, Decker's Ex-Wife from Double Whammy and what is their importance?

Catherine, once married to Decker, takes full responsibility for what she believes was her part in his breakdown, and looks out for him as best she can. When Decker gets himself into trouble, he goes to Catherine for help, unknowingly placing her in danger. Catherine is kidnapped as a result, forcing Decker to do whatever it takes to rescue her.