What is the main conflict in The Monkey's Raincoat by Robert Crais?

The Monkey's Raincoat is the story of L.A. detective Elvis Cole, who is hired by Ellen Lang to find her husband and young son. Elvis discovers that Mort Lang has been killed by wealthy ex-bullfighter Dom Duran, because Duran believes Mort stole two kilos of cocaine. Perry, Ellen's son, is still being held hostage. Elvis tracks own the drugs and stages a raid on Duran's mansion to rescue the boy.