We can't follow them in there.
1 seconds sound clip from the Radar Men from the Moon - Molten Terror (S1E2) movie soundboard.
You can hear this line at 00:11:28.490 in the Blu-ray version of the movie.
Quote context
[...]
- And he won't move very fast carrying that gun.
- There they are. Give them a blast.
- Let's try to keep going. Maybe we could dodge around those rocks and lose them.
- They're still after us. Let's go.
- That looks like a cave. Let's get in there.
- We can't follow them in there.
- Set the ray gun at constant heat, it will melt the cliff and bury them alive.
- Right.
- They turned the ray gun into the side of the cave and it's melting the rock.
- Let's get back as far as we can. Never mind the gun!
- Maybe we can get out along that side.
- We may be able to take care of it.
[...]