1x29 - The Time Tunnel

Tony and Doug arrive in Khartoum, November 2, 1883, in the middle of a battle between British and Arab forces. However, two aliens take them prisoner. The aliens plan to conquer Earth with missiles, and will be ready to launch in two hours - they send a bomb to the Project to prevent them from interfering. Tony is taken to be killed but the alien with him is forced to teleport out when the British approach. Then both guys are transferred out of the cave by the Tunnel staff, where they make contact with Captain Henderson and convince him about the aliens. The three of them attack the cave and manage to stop the aliens, with some help when the Project send the bomb back to the aliens.