Leading BEAGLE, Professor Quilter researched human evolution by synthetically cultivating specimens of what the human race might evolve into. Three creatures were created, named "Alfred", "Russel" and "Wallace" after the naturalist — two of them died; the third thrived initially, but became weakened later on. Near death, the creature, Alfred, was able to transplant the heart of one his guards into his own body, thus prolonging his life. The resultant horror meant that the project had to be closed down in 1975. One of the people involved in that decision was Quilter's friend Brian Rutherford, later the Minister overseeing Liz Shaw's Preternatural Research Bureau (PROBE).
Unable to kill the creature, Quilter had instead secretly reared the beast and educated it, eventually making him his assistant and giving him the name Alfred Emerson. Quilter seemed to ultimately be under the control of the creature, convulsing in pain at times apparently due to the presence of Emerson. PROBE began to investigate the BEAGLE project after a series of deaths involving missing organs — much like the death of the guard in 1975 — including that of the visiting Dr Lancaster. After Quilter's death while under questioning, Rutherford called to the home of Quilter to pay his respects. There, Emerson held Rutherford captive while he revived the body of Quilter, perhaps intending to harvest Rutherford's organs to help the process. Only the intervention of Liz and Col Ackroyd saved the life of Rutherford and killed Emerson. The reanimated body of Quilter survived only a short time, as it was not as evolved as Emerson's. (HOMEVID: Unnatural Selection)
Professor Quilter did not like to be fussed over and, as a result, his funeral was to be "nothing elaborate". He enjoyed croquet. Due to his belief that the Earth was being overcrowded, he believed that humanity had to find a new way to exist. (HOMEVID: Unnatural Selection)