- Bob: "I hardly recognise you without the hat."
- Sherlock/John: "Wasn't my hat."
- Bob: "I love the blog too, Dr Watson."
- Sherlock/John: "Oh cheers!"
- — "The Hounds of Baskerville"
Bob Frankland was a research scientist at the Baskerville Military Base near Dartmoor. He is first seen walking around when Sherlock and John enter the base using Mycroft's government security card. When they are identified as not being who they said they were, Frankland pretends to be an old friend of Sherlock, who he pretends is still Mycroft, and persuades the staff that there must be an IT error. This leads the pair to believe he is a person who can be trusted.
When Sherlock and John are safely out of the base he reveals that he knows exactly who they are as he is a fan of John's blog.
He appears in the pub when John is speaking to Henry's therapist, Louise Mortimer, and ruins John's chances of a date by making it sound as if John and Sherlock are together. This appears, however, to be a mistake of which Frankland is not aware. His presence may suggest that he has been keeping tabs on the pair.
It is later revealed that Frankland had been the one terrorizing Henry Knight for fear that the young man would start to remember the truth of his father's murder, his concern coming from the fact that he had been the one who took Henry's father's life. Frankland held onto the belief that Project H.O.U.N.D. could be revived and restored.
Bob Frankland was originally a friend of the team but was convinced that the drug would one day work, and continued testing it on people. Henry Knight's father realised what Frankland was doing and Frankland was forced to take action. Frankland dosed a young Henry Knight and his father with the drug, while staying safe due to a gasmask. With the other man disoriented, Frankland ambushed him and, after a violent struggle, killed him. Henry only saw the red eyes of the Gasmask and Frankland's T-shirt-with the H.O.U.N.D logo on it and 'Liberty In'.
Twenty years later, Henry started to remember what really happened that night. So Frankland put pressure pads in the ground at Dewers Hollow, so whenever Henry went there he would be dosed with the drug-slowly turning him insane. Whenever Henry did see the hound, he only saw an ordinary dog but the way he expected to see it. By aiming to drive Henry insane, Frankland was also, in part, preventing the man from unveiling too many details of the project, as he was worried about how much Knight knew.
Sherlock Holmes figured out what Frankland was doing and, along with John, Knight and Lestrade, chased Frankland onto the Grimpen mine field where Frankland stepped on a mine and was blown up. The expression on his face before he lifted his foot away from the mine suggests he had already accepted he was going to die and welcomed it as an alternative to imprisonment. After Frankland's death, the project was stopped for good.