“Survival” is episode thirteen of season one of UFO.
A UFO comes in low over the Moon. In one of MoonBase’s spheres, Foster is talking to an Interceptor pilot who is heading home the next day. Outside, an alien approaches and shoots the port of the room where Foster is. Foster sees it start to crack and then blow out. The airlock is closing and Foster tries to keep it open for the other man, but is unable to.
A new port is fitted and Foster wants to know what happened. The pilot’s body is launched into space, then Mark gives Foster the reconstructed port.
At SHADO Control, Foster shows the port and a projectile to Straker and Freeman. The projectile incorporates an unknown alloy. Straker asks if a UFO landed undetected and someone came out and shot at MoonBase. Foster says that a meteorite shower played havoc with their sensors, but the UFO hasn’t had a chance to take off again undetected. He’s ordered the Interceptors to seek and destroy.
Straker says he will go back to MoonBase with Foster, and wants everything on how UFOs disintegrate in Earth’s atmosphere. He wants the Interceptors to seek and observe. It’s thought that the UFOs react to something in the atmosphere, and the Moon hasn’t got one. This is a chance to capture one. He suggests Foster go and unwind, and Foster heads to see a woman.
On MoonBase, they are shown a photo of where the UFO has landed. Two Moon Mobiles are dispatched to it, Foster in command of one and Mark the other. They land and head in on foot. The UFO looks abandoned, and possible damaged on landing.
However, it isn’t unoccupied or damaged. The result of this is that Foster is injured, left without communications and assumed to be dead. Which means no-one is looking for him. And there’s an alien who wasn’t in the UFO as well.