(The BRIGADIER pulls the DOCTOR out of earshot.) A few remain with him. LIZ: Anything from the Mars Probe? Recovery 7 to Mars Probe.
Plan: A: Brigadier; Q: Who investigates a loss of contact with Mars Probe 7? A: Mars Probe 7; Q: What probe is the Brigadier investigating? A: the Doctor; Q: Who realizes signals coming from Mars Probe 7 are of extraterrestrial origin? A: extra-terrestrial origin; Q: What origin are the signals from Mars Probe 7? Summary: While the Brigadier investigates a loss of contact with Mars Probe 7, the Doctor realises signals coming from the probe are of extra-terrestrial origin.