Answering a mayday, the Doctor discovers the dead body of Dr Kaleb Loss on planetoid KX77 in the Bromid system, known as Death's Door owing to its toxic atmosphere. He concludes the researcher died from spacesuit rupture: noting that Dr Loss worked for the Institute for Exo-Contamination Treatment (InFECT), he takes the body several light years to Mustron V, where the Institute is based, curious as to Loss's reason for being on Death's Door. On Mustron V, the TARDIS is forced to land outside the Institute by a forcefield: taking the body in by foot, wearing a spacesuit, the Doctor finds no sign of the remaining four InFECT staff. He is attacked by a large blue biped, which he stuns by pulling an astrograph over on it; he discovers team member Rachel "Red" Barlow in hiding, who tells him th