Harry Dresden isn’t dead…he’s the new Winter Knight for Mab, the Queen of Air and Darkness…there is a big twist and surprise at the end of this tale, involving the grasshopper.
“Rest. Heal. Sleep. I shall most likely kill you on the morrow.”
“You? A Princess Bride quote?” I croaked.
“What is that?” she asked.”
“Go back,” he said.
“Can’t. Stand aside?”
“So it’s like that?” I said.
Fix exhaled. Then he nodded. “Yeah.”
And for the first time in a decade the Winter Knight and Summer Knight went to war.”
“We need to get out,” I said. My voice sounded raw to me. “Trouble coming.”
“No,” said a beautiful Sidhe baritone. “Trouble is here.”
They appeared from behind their veils, one by one, with so much melodrama that I was mildly surprised that they hadn’t each struck some kind of kung fu pose.”
Mouse was introduced in the novel Blood Rites as a small furry puppy rescued from a group of demons. A Tibetan monk employed Harry to recover a stolen litter of puppies believed to be the descendants of an ancient Foo spirit. This meant they were supernatural and special, both qualities that Mouse has shown as he has attained his massive mature size. While Harry returned all the Foo puppies he could find, one particularly scrappy pup hid under his car seat and he was unable to return it. Mouse grows startlingly large by the start of Dead Beat, with his shoulders reaching nearly to Harry’s waist, and kills the former Denarian Quintus Cassius in order to prevent him from killing Harry.
In Proven Guilty Mouse was hit by a car and survived, and he went on to take down supernatural enemies while emitting a faint glow. Mouse has shown an aptitude for detecting dark energies and presences, and he has a strong empathy for humans who display no such dark traces. He also shows intelligence greater than that of any other dog, and seems able to plan, anticipate and comprehend abstract concepts, as well as speech. In addition, in White Night when Harry begins to play the guitar (poorly) as part of therapy for his hand, Mouse gets up off the living room floor and goes into the bedroom, shutting the door behind him. In Turn Coat Mouse intercedes in several violent situations in Harry’s apartment while he is away, defusing them with both his strength and intelligence. He even feigns extreme pain after being shot to teach Molly an important lesson, without any prompting by Harry.
After Mouse exhibits further supernatural abilities in White Night, Bob describes additional powers the dog has, such as a warning bark that awoke an entire building full of people during a fire when the actual alarm could not be activated. This bark can also apparently scare away some supernatural, incorporeal beings. If that doesn’t work, Mouse can actually physically damage a supernatural enemy, usually with his teeth, as has happened with fatal effects during two battles. Also in White Night, Elaine claims that Mouse is a Temple Dog and is stunned he belongs to Harry. Oddly, in Proven Guilty Madrigal Raith exclaims with apprehension that Mouse is “not a dog”. In Small Favor, Nicodemus shows a genuine uneasiness about Mouse’s presence in his meeting with Harry, asking Harry “What is that?” and making sure to keep his shadow in between himself and Mouse.
Despite growing to massive size, Mouse still defers to Mister, allowing the cat to eat before he does and appearing nervous after Harry tells him to take away Mister’s catnip before he gets ill. Harry calls him a cross between a chow, a woolly mammoth, and a “West Highland Dogosaurus.”
The guardian statues that the White Council uses to guard meeting entrances are modeled after Foo Dogs. In Turn Coat, Ancient Mai is shocked that Harry has a Foo dog (exclaiming, “Where did you get such a thing? And why were you allowed to keep it?”), apparently not taking Mouse’s wishes into account. However, she and several other wizards in attendance confirm his reliability as a witness, and Harry uses him and a set of surveillance photos to expose a traitor within the White Council.
In Small Favor, it is indicated that Mouse, in addition to comprehending speech, can show emotion on a level with humans – when told to “take the catnip away” if it makes Mister sick, he seems to indicate doubt; when Thomas claims that what he said earlier about Harry was a joke, Mouse merely flicks his ears and turns away. Also, when Harry jokes about shaking himself dry like Mouse in Michael Carpenter’s home, Michael responds that Mouse would be too polite to do so inside and is promptly proven correct.
In Changes, Mouse is proven to have intelligence as great as any human, and in correct circumstances the ability not only to comprehend human speech but also to communicate as well as any human in his own language. He is also referred to as a “Mountain Ice Demon from the Land of Dreams” by two high ranking Red Court Vampires, as well as Harry’s Fairy Godmother, who, if not afraid of Mouse, is at least wary of his abilities. He also indicates, when the Leanansidhe questioned Harry’s having “won” Mouse, he was the one who “won” Harry, raising the question as to which one actually “owns” the other, although Jim Butcher has stated that Mouse and the Leanansidhe did not mean the same thing when they said “won”. In addition, it is here shown that he has a personality very similar to Dresden’s, evidenced both by his willingness to fight and kill Lea in order to turn the group back to normal after remarking, “That bitch,” and his response to Lea’s comment that he was far from his sources of power to which Mouse is described as shrugging and replying “I live with a wizard, I cheat”. While it’s possible that the similar personalities are a result of living with Harry most of his life, as a puppy Mouse displayed the very Harry-like trait of standing up to things far bigger than him.
In Ghost Story, Mouse is the protector of Maggie Dresden and living with the Carpenter family. He is able to see and physically interact with the spirit form of Harry. The archangel Uriel calls Mouse “little brother” and tells him his task is not yet over. Uriel also assures Harry that temple dogs live for centuries, and Mouse is more than capable of protecting Maggie for a lifetime, even a wizard’s lifetime.