She overhears Vallance and a Cyberman plotting to poison the air supply and warns the Doctor before she is killed by a Cyberman .
Gemma shows them to the airlock but hides in the oxygen room .
Gemma overhears Vallance and a Cyberman plotting to poison the air supply and warns the Doctor before Gemma is killed by a Cyberman .
Gemma shows them to the airlock but hides in the oxygen room .