Addison MacHenry is a peculiar dog with the peculiarity of speech, high intelligence and being able to smell 'peculiar scent'. He also deems himself as extremely sophisticated and extroverted.
He is known as the "seventh pup of the seventh pup in an illustrious line of hunting dogs." Addison lives in Miss Wren's Menagerie, a loop housing peculiar animals. Addison has a pivotal role in the third book, Library of Souls.
|“||I am a dog, yes, but a peculiar one. Why, then, should I be saddled with a common dog's name? My former master called me 'Boxie' and I despised it - an assault on my dignity! - so I bit him on the face and took his name.||”|
–Addison, Hollow City
As a young pup, he once had a master named Addison, who called him "Boxie". Addison (dog) despised that name, calling it an assault on his dignity, so he bit his owner on the face and took his name.
Eventually, he came to live in Miss Wren's menagerie.
When Jacob and his friends arrive at the menagerie, Addison calls off Grunt before introducing himself. He tells the peculiars that Miss Wren had flown off to help ymbrynes in London, but invites them further in so that they can eat and regain their strength. He calls for the other peculiar animals in the menagerie to come out and meet the peculiars, and introduces some of them.
Addison, Deirdre, and Grunt go off to make an elixir for a sick Claire, then with the other animals serve the rest of the peculiars food. When Olive asks Addison where more animals are, all of the animals' moods wilt and Addison decides to tell Jacob and his friends the story of how peculiar animals are near extinct, showing them the menagerie's cemetery. He then speaks of Miss Wren and how she went to London to aid other ymbrynes.
He is shocked to see that "Miss Peregrine" also remains uncaptured by the wights (unaware, like everyone else, that the bird shown to him is actually Caul). Upon learning that she apparently cannot change back to human form, he examines her, and announces that she has been poisoned by something that keeps her in bird form. He tells the peculiars that if she does not receive help to turn back soon, she will remain a bird with her human side completely lost forever, giving Olivia as an example.
While the peculiars are preparing to leave, Addison meets Jacob and Emma at the top of Miss Wren's tower to show them the way out of the forest, and also requests that they send Miss Wren back if they should encounter her. He then allows Emma to scratch the top of his head, but objects when Jacob tries to pet him. He sees off the group with the rest of the animals, and for one last favor asks Emma to light his pipe as he has not had a real smoke for years.
Shortly after, the menagerie was raided by wights and Addison left to find Miss Wren. At the end of the book, he appears having rescued Jacob and Emma from being taken by the wights.
Addison, after the wights raid the menagerie, had escaped and tracked Jacob and Emma down to the trains after the rest of their friends were captured by wights. He draws two wights' attention to them after they find an injured Sergei Andropov, but luckily they are saved by Jacob's hollow, giving them enough time to jump on a train.
On the train, Addison opens a window and starts following the scents of Jacob and Emma's kidnapped friends. At Emma's question, he tells them about the raid on the menagerie and what happened to Fiona and Claire: they and the animals were gassed out of their hiding spots, with Deirdre being shot, Claire being kidnapped, and Fiona falling off a cliff. He and Emma exchange condolences. He goes on to explain how he left for London to find Miss Wren, and her pigeons led him to her hideaway. He had arrived after the wights began raiding the building, and after the wights took the peculiars to the present and the underground he followed them. He was able to drag Jacob and Emma away from the train and the wights after the Bone Brothers' scream. He wanted to save Miss Wren first and foremost, but Jacob and Emma were the more realistic save, that he could pull off.
Because of his pride, he refused to stay quiet when a pair of normal teenagers come into their train car, causing the boy to faint and the girl to scream, thus alerting a wight at the adjacent car of their presence. He, Jacob and Emma run with the wight chasing them, during which he gets briefly entangled in a lady's stocking. Again, he causes someone to faint by speaking. He catches peculiar scent once more in a comic convention, but after a bit loses it as it has suddenly disappeared.
Addison is a boxer dog, holding a pipe in his jowly mouth and wearing a pair of round, green-tinted glasses. When he stands on his hind legs, he is almost as tall as Enoch.
Addison has great dignity and pride, and sometimes speaks with higher level diction. He becomes offended when treated as a common dog, considering it a humiliation, and cannot act as one for much time even when it is required in front of normals- speaking up when he has had enough. He is "easily distracted by the topic of his own greatness, even when pressing matters were at hand." He still does retain some behaviors of any dog.
Addison dislikes running away, and is extremely loyal to his ymbryne, Miss Wren. In The Desolations of Devil's Acre, Jacob thinks to himself that if every peculiar were as loyal to ymbrynes as Addison is, Jacob would have no doubt about their chances against Caul. Deirdre also calls him a "regular Doctor Dolittle," as he used to treat the other animals in the menagerie when they were sick.
Addison is a dog with the ability to speak and has a seemingly high IQ. He also has a nose for peculiars (he can smell their unique scent, there for extremely helpful in tracking any peculiar, animal or human). He has a very high opinion of his ability, stating that he can "find a peculiar in a hollow-stack, an ymbryne in an aviary."