Will Henry is the loyal apprentice of the Monstrumologist and the author of the folios that have been published.
History of William James Henry
Will Henry was the son of James and Mary Henry, of the village of New Jerusalem. His father, James Henry, served the doctor as his assistant until his death in a house fire. After the fire, out of fealty and respect for James Henry, Dr. Warthrop took Will Henry in as his assistant. At the start of the series, Will Henry has been living with the doctor for a little under a year, and was 12 years old. He accompanies the doctor on his expeditions and adventures - a dutiful and loyal assistant.His real name is not William James Henry, though you never find out what his name is.
In the beginning of the series Will Henry is the loyal apprentice of the Monstrumologist, Pellinore Warthrop. He's a bit of a "yes sir" kind of person, and although he's intelligent, he tends to be timid and keep to himself, doing whatever Warthrop tells him. However, by the end of the third book he has begun to come out of his shell- but the many gruesome acts of violence that he has witnessed has begun to have its effect on him, making him harder and destroying the childish innocence. In the fourth book, the change is clear, Will's lack of remorse or the morals that used to guide him now obvious. He now has lost any hesitancy when it comes to committing murder or other violent crimes, excusing it as "necessary" to save himself and those closest to him.
Dr. Warthrop, Master of Will Henry
Dr. Warthrop took Will Henry in after his parents died in a house fire. Will Henry generally refers to Dr. Warthrop as the monstrumologist, my master, or the doctor; never his full name. As Will Henry is a child, Dr. Warthrop scolds him often, sometimes even yelling as in the case of Will Henry's 'incisive 'yes, sir!'. Although there is no direct reference, Will Henry feels the Doctor is like a father, shown in the end of The Curse of the Wendigo when they hold each other's hands for comfort like a father and son. Dr. Warthrop often tells Will that Will's services are indisputable to him. Will frequently comments that he doesn't love the doctor, but he does show a degree of care for him, often urging him to rest and eat after days of the doctor's research. However, Will also thinks of the doctor as his "mentor - and tormentor" - and sometimes resents the doctor's actions towards him.
The doctor himself cares for Will, as when they camp in the Canadian Bush, the doctor holds Will on a particularly cold night to keep him warm. In an argument between Muriel and the doctor, when Muriel tells him that one day Will Henry will leave him, the doctor replies "Will Henry will never leave me", and then checks on him afterwards. He also broaches the subject once at Will's bedside, seemingly stoic while Will Henry is terrified and says that his place is there, with the doctor.
Dr. Warthrop is also Will Henry's mentor in the science of Monstrumology, teaching him the ways of a monstrumologist and how to live. Many times over he gives Will Henry "valuable" advice, such as 'when a person of the female gender wants to show you something, run away in the other direction' and 'do not love, it will tear you apart'.
In the fourth book he becomes rebellious towards the doctor.He often blames the doctor for the decisions he makes, claiming that if the doctor hadn't taken him in he wouldn't have had to make those decisions.He recognizes that he and the doctor are the similar, needing each other to ebb the loneliness and that they are both scared lost boys.
When Will is eighteen, he leaves the house they had shared. While the exact reason he left isn't revealed, it can be assumed that it was due the increasingly strained relationship between Warthrop and Will Henry, that must have finally snapped.
In dramatic turn of events, when Will is in his mid-thirties and Warthrop is in his fifties, Will comes back to the house Warthrop lives in, and ends up killing him. Before that, he describes him as "pathetic", saying that after Will had left,Warthrop was unable to function, becoming even more obsessed and reclusive.
Will Henry, like his master, has a hatred for Kearns and dislikes his methods of dealing with the issues they face. John Kearns does not appear to care for anyone- at least anyone whom Will meets- and Will despises this in him. However, John Kearns may have been foreshadowing for Will's character development, as in the fourth book, Will Henry starts to kill just as easily as John Kearns had. John Kearns final appearance in the series is in the third book, when Will Henry kills him, despite Warthrop telling him earlier that to kill Kearns would be unnecessary and cruel. This is a huge development for Will, for now he is not only defying Warthrop, he is killing when it is not absolutely necessary. This further supports the theory that Kearns symbolizes Will's future self, as Will after Will kills him, he becomes more like him.
Will Henry shared a strong bond with Malachi due to both of them losing their parents to gruesome deaths. Henry is able to empathize with Malachi situation and understands his anguish over the lose of his family.
Lillian Trumble Bates
Lilly Bates and Will Henry meet when she is thirteen and he is twelve, as she is the niece of Warthrop’s old master. When they are children, Lilly tends to exasperate Will Henry with her energy and eagerness to learn about Monstrumology. She is very passionate and brutally honest, often coming across as rude. Will says he has never met anyone like her, and while at first he isn't very fond of her- or perhaps she simply scares him-, they eventually fall in love when he is sixteen and she is seventeen. However, she grows more and more nervous around him, and when he tries to leave with her, she refuses, saying that he scares her and that he is missing something (presumably, she mean his humanity). He ends up striking her across the face,and any chance they had at a relationship ends then.
They don’t see each other again for many years. In fact, as far as we know, the next time they meet is at her father’s funeral in the year 1929. However, Lilly does at that time know that Will killed Warthrop by feeding him to the monstrous creature he owned, implying that they must have been communicating by letter if they had not seen each other in person recently. They chat for a while after his funeral, although they both seem distant. Lilly’s current husband is also present, whose name is inferred to be William James Henry, meaning that Will’s true name is never revealed to the reader. In the end, they part sadly, and we never know if they meet again.