Even though Doc, an old drunkard German music teacher, represents the world of logic and rationality, he understands the mystical side of life at the same time. In Chapter Nineteen Peekay summarizes his character: "Doc was calm and reason and order." However, Doc tells Peekay that when truth is not at stake, it is better to choose mystery above logic. Doc's relationship with Peekay begins when they meet in the hills behind Peekay's home in Barberton-Doc moved to South Africa from Germany fifteen years previously, and his speech is sprinkled with German words, and bizarre words of his own invention (such as "absoloodle"). Doc loves coffee, but he loves Johnny Walker whisky even more. Doc was a famous concert pianist in Germany, but during a concert in Berlin in 1925 he froze up while playing Beethoven's Symphony Number Five, and has been terrified to play every since. Doc becomes Peekay's piano teacher, general mentor, and best friend.

Doc gets arrested and has to spend the years during World War II in the Barberton prison since he did not ever register as a foreign alien. The first assumption of the town, however, is that he must be a German spy. Doc is nothing of the sort, and he thus represents the ultimate impossibility of pigeonholing a person according to their exterior identity. He continues to mentor Peekay while in prison, and he barters giving piano concerts (something which he hates doing) in order to be allowed to see Peekay each day. He tells Peekay that he loves him more than his life. Once Doc is liberated from prison, he and Peekay return to their roaming about the Barberton hills. One of Doc's chief hobbies is to document different kinds of cacti, and he teaches Peekay all of the prolific Latin nomenclatures. Together Doc and Peekay discover the "crystal cave of Africa," where Doc takes himself to die. Doc's death has a great impact on Peekay, who is only accustomed to brutal death. Peekay describes his and Doc's love for one another as "so fierce that it burned like a flame inside of us." Doc teaches Peekay confidence, a love of music, a love of learning, a love of Africa, and how to conquer his fears.