..at last restores some of the mystery and enigma that had been a trademark of the first series. Great stuff, ably directed by Val Guest, whose bouncing alien spheres are a joy.
(Richard Houldsworth, TV Zone, 1993)
...it features two women wearing smug expressions and very little else. Other than this the story has very little going for it. 5/10
(Anthony McKay, DWB, 1994)
An exciting episode which ends with a desperate predicament that is resolved in an unexpected way. The Voice Probes are excellent. A-
(Chris Bentley, SFX 20, 1996)
As usual, Martin Landau turns in a fine performance, adding deeper layers to Koenig's personality. Here the Commander is as desperate as the viewers have ever seen him. Tony Barwick's screenplay has the benefit of being completely original. The concept and execution of the bouncing spherical voice probe computers are outstanding and the idea of the aliens breathing chlorine adds some much appreciated believability to the season.
(John Kenneth Muir, Exploring Space: 1999, p126)
The merits of this episode highly outweigh any minor criticisms. The happenings on the planet are intriguing and enjoyable. The climax is dramatic and effective, followed by well-conveyed elation, which successfully translates to the viewer. 9/10
(Bob Wood, The Future Is Fantastic, 2001)