Creepy looking and sounding aliens seek The Robot.
An outstanding episode of LIS which proves that the second season still has some knockout classics (see also Blast Off Into Space, The Ghost Planet, The Deadly Games Of Gamma Six, The Prisoners Of Space, The Dream Monster, The Golden Man, Cave Of The Wizards, Trip Through The Robot, The Colonists, The Galaxy Gift).
The creepy aliens are a knockout and that wonderfully photographed scene of them lurking around the Jupiter 2 campsite at night would have to rank as one of LIS's finest moments. Outstanding music cues as well.
These exact same aliens would return in The Galaxy Gift and their distant cousin seems to be onboard the submarine Seaview in the Voyage to the Bottom of the Sea episode titled - The Shadowman.