Miriam Monroe and John Conrad are two young scientific workers who, independently of each other, have discovered a chemical called exonite. Miriam discovered it while searching for a cure for cancer, while Conrad used it as a basis for a powerful explosive.
| Actor | Role |
|---|---|
 Ethel BarrymoreMiriam Monroe | Miriam Monroe |
 William B. DavidsonJohn Conrad | John Conrad |
 Harry NorthrupAlbert Bernard (as Harry S. Northrup) | Albert Bernard (as Harry S. Northrup) |
 Frank CurrierRandolph Monroe | Randolph Monroe |
| WWilliam BlackBradford Duncan | Bradford Duncan |
| CCecil OwenEric Johansen | Eric Johansen |
 Frederick TruesdellProf. Poole (as Fred C. Truesdell) | Prof. Poole (as Fred C. Truesdell) |
| RRedfield ClarkeMaj. Gen. Foster (as Redfield Clark) | Maj. Gen. Foster (as Redfield Clark) |
| RRudolph De CordovaWilliams | Williams |
| WW.M. ArmstrongCapt. Herbert | Capt. Herbert |