ThefourthseasonofAllCreaturesGreatandSmallwillpickupinspringtimeof1940withchangeonthehorizonforeveryoneinSkeldaleHouse.JamesandHelenwonderwhentherighttimemightbetostartafamily,notknowingwhetherornotJameswillbecalleduptoserveintheRAF.Tristan’sabsenceisfeltbyall,butnoonemorethanSiegfriedwhoattemptstoholdthegrowinghousehold,andhimself,togetherashebravesthisnewworld.MrsHallandHelen’sfriendshipblossomsastheylooktothefutureandnewtraineeveterinarystudentRichardCarmodyarrives,causingcomplicationsinthehouse.