For the hallucination that identifies himself as "Walter" in Guardian Angels see Old Man.
Walter is the father of the teenage faith healer Boyd in the episode House vs. God. He was portrayed by actor William Katt.
As Boyd was underaged, his father had to approve all treatment decisions. Both he and his son are very devout and believe that God can communicate and work through people, and he was convinced that Boyd had a gift of being able to communicate. However, the team was convinced Boyd was merely having auditory hallucinations that were the product of a disease. When they discovered that Boyd had tuberous sclerosis, it seemed to confirm the team's opinion as the tumors can press on the brain to cause hallucinations and seizures. However, despite the diagnosis, both Boyd and Walter believed that this disease was how God communicated with Boyd and, as the symptoms could be managed, they refused further treatment.
However, Gregory House was still suspicous as Boyd had symptoms that did not appear to be explained by the tuberous sclerosis. He pressed for another answer and realized he might have one when a patient of Wilson's got better after she had contact with Boyd. He also noted Boyd had been drinking large amounts of water. He thought that Boyd might have herpes encephalitis, a sexually transmitted disease. However, Boyd refused any treatment or tests, saying it was what God wanted. Robert Chase, who had been sympathetic to Boyd, pointed out that they were merely doing a physical examination to look for the sores typical of the disease. Boyd pleaded with his father who replied:
- "I trust God. You... I trust as much as any teenage boy."
- ―Walter
The doctors found the sores, which were promptly treated.