▁episodes . ▁ ▁Plot ▁ ▁The ▁T ARD IS ▁makes ▁a ▁b um py ▁landing ▁on ▁the ▁Moon ▁in ▁the ▁year ▁ 2 0 7 0 ; ▁dressed ▁in ▁spaces uits , ▁the ▁Second ▁Doctor ▁and ▁his ▁compan ions ▁Ben , ▁Pol ly ▁and ▁Jam ie ▁vent ure ▁outside ▁to ▁explore ▁the ▁low - gravity ▁environment . ▁While ▁they ▁play , ▁Jam ie ▁is ▁injured . ▁ ▁Some ▁workers ▁from ▁the ▁nearby ▁Moon base ▁find ▁Jam ie ▁and ▁bring ▁him ▁inside ▁for ▁treatment ▁while ▁the ▁remaining ▁T ARD IS ▁crew ▁follows . ▁The ▁time ▁trav ellers ▁learn ▁that ▁the ▁Moon base ▁uses ▁a ▁machine ▁called ▁the ▁Gra v it on ▁to ▁track ▁and ▁manage ▁weather ▁on ▁Earth . ▁Their ▁arrival ▁is ▁ill - tim ed , ▁as ▁members ▁of ▁the ▁international ▁crew , ▁led ▁by ▁the ▁b ull ish ▁Hob son , ▁have ▁begun ▁to ▁collapse ▁under ▁the ▁influence ▁of ▁an ▁unknown ▁path ogen . ▁ ▁While ▁International ▁Space ▁Control ▁quar ant ines ▁the ▁Moon base , ▁the ▁Doctor ▁starts ▁to ▁investigate . ▁Before ▁he ▁dies , ▁the ▁station ' s ▁patient ▁zero ▁– ▁their ▁staff ▁doctor , ▁Evans ▁– ▁r ants ▁about ▁a ▁" sil ver ▁hand ". ▁Another ▁crew ▁member , ▁Ralph , ▁then ▁van ishes ▁in ▁the ▁food ▁stores , ▁and ▁the ▁crew ▁learn ▁that ▁their ▁radio ▁transm issions ▁are ▁being ▁monitor ed ▁from ▁elsewhere ▁on ▁the ▁Moon . ▁ ▁Meanwhile , ▁in ▁the ▁sick bay , ▁a ▁fe ver ish ▁Jam ie ▁begins ▁to ▁r ant ▁about ▁a ▁"