Ohn Chang, an overwrought father hires Khan to find the man who murdered his daughter.  Keye Luke guest stars on Khan (Khigh Dhiegh) as a disconsolate father, convinced that his daughter's death is the doing of a young medical intern. Ohn Chang (Luke), unaware of his daughter's dissolute life, seeks Kahn's help in establishing the doctor's (David Wilson) guilt.

Khan undergoes some pangs of conscience when a former British agent stands accused of diamond robbery and the evidence is overwhelming. The man saved once Khan's life.

The killing of Khan's friend, a physician, is linked to an international crime syndicate, dealing in gambling and narcotics which appears to be moving into California. During a Hong Kong-San Francisco telephone call, both caller and recipient are shot dead and Khan discovers that the key to the mystery lies with a man who returns to San Francisco for his daughter's wedding.