Episode FiveSeries Episode Number: 348
World Premiere: Sat 5 May 1973 - 5:51pm BST [BBC One] (United Kingdom)
Running Time: 22 minutes 31 seconds
9.70 Million (UK)
Chart Position: 21 () (UK)
Recorded on Mon 19 Feb 1973 in TC1
Archive State: PAL 2 VT
Desperate to prevent the Daleks from releasing their plague, the Doctor, Jo and the Thals infiltrate their base. But the Daleks detect the intruders!