Bill Holmes rescues Rinty from a car wreck not realizing that there is a stolen $50,000 diamond necklace hidden in the dog's collar.
| Actor | Role |
|---|---|
 Rin-Tin-TinRinty | Rinty |
 Matty KempBill Holmes | Bill Holmes |
 Evelyn PierceMary French | Mary French |
 Philo McCulloughJoe French | Joe French |
 Tom DuganEd Mack (as Tommy Dugan) | Ed Mack (as Tommy Dugan) |
| AAllan CavanPolice Chief | Police Chief |
| GGrover LigonScar | Scar |