The Brigadier calls in a full UNIT force to deal with the giant maggots while the Doctor infiltrates Global Chemicals to find out what is really going on.
Quest roles:
Richard Franklin(Mike Yates), Nicholas Courtney(Brig. Lethbridge-Stewart), Terry Walsh(Doran (uncredited)), John Levene(Sergeant Benton), Brian Justice(Yate's Guard), Jerome Willis(Stevens), Stewart Bevan(Clifford Jones), Tony Adams(Elgin), Ben Howard(Hinks), Ray Handy(Milkman), John Dearth(Lupton), Jean Burgess(Cleaner), Mitzi McKenzie(Nancy)