cat ons ▁fall ▁back ▁to ▁the ▁salt ▁water , ▁except ▁for ▁one ▁tra pped ▁in ▁a ▁London ▁Under ground ▁tunnel . ▁The ▁Doctor ▁and ▁Sarah ▁Jane ▁search ▁for ▁it , ▁and ▁the ▁Doctor ▁plays ▁a ▁pic colo ▁to ▁calm ▁his ▁n erves . ▁The ▁P es cat on ▁retre ats ▁at ▁the ▁sound . ▁Professor ▁Em erson ▁helps ▁the ▁Doctor ▁build ▁a ▁high ▁frequency ▁sound ▁trap ▁inside ▁a ▁se wer , ▁and ▁Z or ▁is ▁l ured ▁there ▁to ▁be ▁destroyed ▁as ▁the ▁planet ▁P es ca ▁dis integr ates ▁in ▁its ▁orbit . ▁Without ▁Z or ▁to ▁control ▁it , ▁the ▁P es cat on ▁invasion ▁ends . ▁ ▁Re leases ▁ ▁Doctor ▁Who ▁and ▁the ▁P es cat ons ▁was ▁released ▁on ▁LP ▁and ▁c ass ette ▁by ▁Ar go ▁( a ▁division ▁of ▁De cca ) ▁in ▁July ▁ 1 9 7 6 , ▁re - re leased ▁on ▁CD ▁in ▁ 1 9 9 1 ▁by ▁Silva ▁Screen ▁Records , ▁and ▁re - re leased ▁again ▁by ▁BBC ▁Audio ▁on ▁CD ▁on ▁ 3 ▁January ▁ 2 0 0 5 . ▁The ▁ 2 0 0 5 ▁CD ▁release ▁includes ▁the ▁complete ▁original ▁programme ▁on ▁disc ▁one , ▁and ▁a ▁new ▁interview ▁with ▁Elisabeth ▁S lad en ▁recorded ▁on ▁ 2 1 ▁May ▁ 2 0 0 4 ▁on ▁disc ▁two . ▁▁ ▁It ▁was ▁re - re leased ▁as ▁an ▁LP ▁– ▁this ▁time ▁on ▁col oured ▁vin yl ▁and ▁as ▁part ▁of ▁a ▁two - album ▁Doctor