s ▁where ▁the ▁Black ▁Guardian ▁comp els ▁T url ough ▁to ▁kill ▁the ▁Doctor . ▁ ▁The ▁serial ' s ▁production ▁was ▁bes et ▁by ▁problems ▁caused ▁by ▁industrial ▁action ▁taken ▁by ▁elect r icians ▁at ▁the ▁BBC ▁during ▁film ing . ▁It ▁was ▁eventually ▁finished ▁three ▁months ▁behind ▁schedule , ▁but ▁the ▁un av ail ability ▁of ▁several ▁actors ▁for ▁new ▁film ing ▁dates ▁forced ▁the ▁production ▁team ▁to ▁rec ast ▁their ▁parts ▁at ▁short ▁notice . ▁En light en ment ▁aver aged ▁of ▁ 6 . 8 ▁million ▁view ers ▁per ▁episode ▁on ▁its ▁first ▁transmission ▁and ▁received ▁generally ▁positive ▁reviews ▁from ▁critics . ▁ ▁Plot ▁Following ▁inter ference ▁from ▁both ▁the ▁White ▁and ▁Black ▁Guard ians , ▁the ▁Fif th ▁Doctor ▁material ises ▁the ▁T ARD IS ▁in ▁what ▁appears ▁to ▁be ▁the ▁hold ▁of ▁an ▁Edward ian ▁y acht , ▁though ▁the ▁Doctor ▁sens es ▁something ▁is ▁am iss . ▁The ▁human ▁crew ▁have ▁no ▁idea ▁how ▁they ▁got ▁there ▁nor ▁where ▁they ▁are , ▁but ▁know ▁they ▁are ▁helping ▁their ▁captain ▁to ▁run ▁a ▁race . ▁The ▁Doctor ▁and ▁his ▁compan ions , ▁T eg an ▁and ▁T url ough ▁discover ▁that ▁the ▁ship , ▁and ▁several ▁other ▁historical ▁Earth ▁ships , ▁are ▁compet ing ▁in ▁a ▁solar ▁sail ▁race ▁through ▁the ▁Sol ar ▁System . ▁The ▁ship ' s ▁officers ▁reve al ▁themselves ▁to ▁be ▁" E tern als ", ▁compared ▁to ▁the ▁Doctor ▁and ▁the ▁humans ▁as ▁" E ph emer als ". ▁The ▁E tern