Jessica Willamy (also known as Summer) was Denny Glass' girlfriend. He went missing in San Francisco just prior to the Human Be-In concert in 1967. She feared that he had somehow gotten mixed up with Blue Moonbeams, a then-new and dangerous version of LSD. Ben, Polly and the Second Doctor became involved in Jess' search for Denny.
She discovered he had been recruited by the Combine, who were spreading Blue Moonbeams as they saw the Summer of Love and counterculture movement as a threat. The source of the drug, a Colour-Beast the Combine had captured, was freed by the Doctor, Ben and Polly. Denny warned Summer to leave San Francisco and hide to avoid the Combine's wrath.