Quatermass plans to use an invention of Roney's, an "optic-encephalogram", to see these visions. The device will record impressions from the optical centres of the brain, in effect showing whatever the subject is seeing, hallucinatory or not. He wears the device and goes into the craft, but it is Roney's assistant, Barbara Judd, who is affected most. Placing the device on her, they record what she "sees"—a violent, bloody purge of the Martian hive, to root out unwanted mutations.