— Commander John Koenig Barbara Bain — Doctor Helena Russell Also Starring Catherine Schell — Maya Featuring Tony Anholt — Tony Verdeschi Zienia Merton — Sandra Benes Guest Stars James Laurenson — Patrick Osgood Pamela Stephenson — Michelle Osgood Also Featuring Jeffery Kissoon — Doctor Ben Vincent Lloyd McGuire — First Mining Engineer Brendan Price — First Security Guard (Morgan) Alan Hunter — Eagle One Co-Pilot (Bill) Nova Llewellyn — First Alphan Woman Uncredited Artists Saul Reichlin — Second Mining Engineer Karen Ford — Nurse Felicity York — Second Alphan Woman Robert Reeves — Peter Quentin Pierre — Second Security Guard Jenny Cresswell — Command Centre Operative Music The score was re-edited from previous Space: 1999 incidental music tracks composed for the second series by Derek Wadsworth and draws primarily from the scores of "The Exiles" and "One Moment of Humanity". Production Notes "Catacombs of the Moon" is a 'Helena Double-Up' script and was produced simultaneously along with "The AB Chrysalis". Series regulars Barbara Bain, Tony Anholt and Zienia Merton carried the majority of the action. Martin Landau's brief scenes were confined to the Eagle command module; his only interaction with Bain occurred via TV monitor in the epilogue. Catherine Schell's two small contributions amounted to a cameo appearance. The episode is set primarily in the standing Alpha sets with moderate filming in the Stage 'M' cavern sets originally built for "The Metamorph". This episode featured the return of Zienia Merton after a three-month absence; the actress had left the programme after filming "One Moment of Humanity" because of her reduced involvement (sometimes only a half-day's work) and her new non-contracted 'day-player' status. Merton recounts that Barbara Bain had telephoned and asked if she would consider meeting with Gerry Anderson and Fred Freiberger to discuss her returning to the series. Bain's motivation was that she and Martin Landau would be on holiday for the majority of the shooting of an uncoming episode ("The Beta Cloud"). As this would result in a very brief appearance by the series' stars, the Landaus feared long-term fans would be alienated when tuning in and not seeing any familiar faces from the first series. Guaranteed a more involved role in the series (though still no contract), Merton accepted the offer. From this time forward, her character was referred to on-screen only by the diminutive 'Sahn' (sometimes 'Sahn Benes' in script character lists). In the shooting