Ian Berriman of "SFX" felt that it was "churlish" to criticise the Loch Ness Monster effect when the story "gets so much right, including first-class direction, pitch-perfect performances and a hauntingly eerie, folky score". He also was positive towards the design of the Zygons and their spaceship, though he found their scheme far-fetched. Christopher Bahn, reviewing the story for "The A.V. Club", described it as "fun" but noted that it could be formulaic instead of trying to be "groundbreaking"; he criticised the scene in the second episode in which Broton tells Harry everything about the Zygons, which did not leave much surprise for the later episodes. Nevertheless, he praised the cast, the action sequences, and the Zygons, which he described as "wonderfully surreal triumph of Doctor Who visual design", though otherwise they functioned as a typical monster-of-the-week.