Dr Smith and Will befriend an old miner named Nerim. After a series of earthquakes indicates that the planet is breaking up, Dr Smith tries to convince them that it is merely the effects of mining, and no harm will come to the planet. John informs him that he is wrong and that the Robinson family will be departing within the day. It is a race against time to escape the crumbling planet.
Elenco: Guy Williams , June Lockhart , Mark Goddard , Marta Kristen , Angela Cartwright , Bill Mumy , Jonathan Harris , Dick Tufeld , Bob May .