The Professor and Major West become trapped in quicksand and Dr. Smith cowardly refuses to help them. Once safe, Don threatens to leave Smith behind once they've drilled enough deutronium fuel to take off. To secure his passage off-world, Smith attempts to steal the fuel, but he soon finds a strange plant which duplicates anything that is put inside its flower – including a canister of fuel. Smith then returns with more than enough fuel for everyone to return to Earth, but the duplicate canister is found to be made of useless vegetable matter. Meanwhile, having absorbed the deutronium, the flowers grow to enormous size and spread everywhere. Attracted by their beauty, Judy is lured closer to a flower and it absorbs her. Later, a plant-controlled clone of Judy appears who steals the rest of the fuel and threatens to kill the real Judy if the Robinson don't provide more fuel for the hungry plants.