Sir Rupert Gale was affiliated with Penelope Fittes. His father had helped Marissa Fittes; and, now, Rupert Gale served Penelope. His role was to teach agents in sword fighting and martial arts.
He first appeared (Book 2) as an unnamed "collector" at Julius Winkman's auction for the Bone Glass. He had much interest on buying the artifact but Anthony Lockwood and Lucy Carlyle, wearing masks, had stolen it. Gale gave a chase but the two escaped.
He appeared next (Book 3) as a companion of Penelope Fittes meeting Lockwood's team, officially, in the carnival. There, he immediately hinted that he recognized the chins of the pair - Lockwood and Carlyle - who attacked the auction of Winkman. Soon at the parade, the carnival attack happened when two conspirators threw ghost bombs at the gathering crowd. Sir Rupert Gale, after Lockwood and Carlyle, gave a chase to the remaining assailant (the other one was killed by Steve Rotwell earlier). The assailant was able to escape and left the pursuing trio alone. Gale, found a chance to take revenge, initiated a combat against Lockwood that was quickly halted when other people have appeared behind them. The two looked forward for a chance to finish the duel.
After some time of not being seen by Lockwood and co., he and Penelope Fittes (Book 4) surprised the agents of Lockwood & Co. at 35 Portland Row with a visit at breakfast. There the two asked the small agency to join Fittes Agency. But when the youths declined, the pair presented their threats and warnings for the youths to stop investigating the gates to the Other Side. From this point on, Rupert Gale was clearly a fixer, the one who does the dirty work, of Penelope Fittes.
Penelope and Rupert Gale had been more aggressive since their visit at 35 Portland Row (Book 5). He threatened Holly Munro when the girl was out for groceries. He arranged the murder of Adam Bunchurch - the head of a small agency who rejected Penelope Fittes. And, he ordered some men to rough up George Cubbins to stop Lockwood and co. from researching further about the Other Side. However, his beating of Cubbins pushed Lockwood and co. to further research by sneaking in the Orpheus Society.
Deciding to finally finish Lockwood and co., Rupert Gale asked a recently released Julius Winkman to prepare an attack at the home/base of operations of Lockwood. Hiring Winkman kept Gale's hands, and Penelope's, clean. He joined in the siege of the house. The youths escaped, when they were overpowered, by hiding in the Other Side. Rupert Gale was the only one to recognize the cause of disappearance of the youths and so he destroyed the gate (to the Other Side) that the youths used.
A day later after the siege of 35 Portland Row, Rupert Gale confronted again Lockwood and co. within the Fittes House in the Hall of Pillars. The youths, who earlier had found odd weapons, shot blasts that shattered the Relic Columns, where infamous ghosts were kept. One of the ghosts called the Gory Girl snatched and killed Rupert Gale.
He was an adult young-looking man. His age was not given but definitely past the Talent age. He wore a mustache. And, he was later known for wearing a strong sent of aftershave.
He carried a sword-stick (a.k.a cane-sword = sword hidden within a cane/walking-stick) as his primary weapon.