Harrison Chase was an eccentric millionaire whose obsession was botany. He was a madman with a disdainful attitude toward human life, and favouritism over another form of life, in this case plant life.

Through his vast resources, Chase learned that the seed pods of a Krynoid, an intelligent form of alien plant life, had been found in Antarctica. A collector of rare specimens, Chase became obsessed with obtaining a sample, and successfully acquired one. He allowed the Krynoid to possess one of his henchmen, who began to mutate into a Human-Krynoid hybrid. As the monster grew in size and power, Chase too became possessed by the Krynoid.

Convinced of a future where Krynoids are the dominant life form on Earth, Chase aided the monster in earnest. By this time, the Fourth Doctor and Sarah Jane Smith were trapped on Chase's property. Chase eventually captured Sarah and attempted to kill her by throwing her into a compost shredder. The Doctor stopped him, and the two fought, until Chase fell into the shredder and perished.