The "Brigadier" (Nicholas Courtney) is having trouble contacting the returning Mars probe so drafts in the "Doctor" (Jon Pertwee) and "Miss Shaw" (Caroline John) to try and get to the bottom of the mystery. With a bit of help from the space centre director "Cornish" (Ronald Allen) he quickly concludes that there is some extra-terrestrial shenanigans going on - especially when the crew do, eventually, arrive and seem to need enormous amounts of radiation in order to survive. A return trip to space to retrace their steps seems to be in order, but there appears to be an uncanny number of obstacles being thrown in the path of his scientific investigations. Is there someone on the inside who knows more than they are letting on - and is there an ulterior motive? This is another rather plodding seven-parter that takes it's time to get going, and when it does all rather underwhelms. It's fairly obvious who the antagonists are from episode three and until the tail end of the series, there's not really enough action happening. Director Michael Ferguson clearly hadn't the budget, or the notion, for special effects and this comes across as merely an half-decent murder mystery, with an underlying moral message, that only has a very slight sci-fi influence. It's not really a time-travelling adventure for "Dr. Who" with a solid story for us to get our teeth into. I'm still struggling to warm to "Shaw" too - though her role here is somewhat third wheel to Courtney's - and the military's - more prominent ones and to be honest I found this just a little bit of a wordy slog.