After the wreckage of a human space ship is found, a cute dog and a less cute monster show up. Jonathon Harris continues to develop his 'Dr. Smith' character into an incompetent, childish fool rather than an immoral, conniving (and interesting) villain. In this case he continues to maintain that the dog is an enemy alien in disguise, which could have been entertaining if the writers made an effort to have the dog to 'act suspiciously' when Smith is watching (but instead it is just acts like normal dog and Smiths paranoia is just a simplistic running joke). The coincidental arrival of the monster is never explained (although John delivers some pseudo-science about mutants that can absorb people). Continuity problems continue to plague the series (the writing was getting pretty sloppy by now) and the future of the dog is unclear, as he seems to join the Robinsons but is never seen, or even referred to, again (perhaps he was absorbed by a mutant off-camera). Not worth the viewing time for anyone but forgiving fans and dedicated series completists.