Arthur Josiah Trent was the father of Dan and Amy. Arthur Trent was the father of 7 year-old Amy and 4 year-old Dan Cahill. He was killed in a house fire, along with his wife, Hope Cahill. The fire was presumably set by Isabel Kabra, an enemy of the Madrigals. As a result, his two children, Amy and Dan, became orphans.
Arthur Trent was born to a family with close ties to the organization known as the Vespers. He was raised to hate the Cahills and think of them as weaklings. He attended West Point Military Academy, and was roommates with Eisenhower Holt, as revealed on Card 145 and on a Vesper hunt mission (game). He found evidence that Eisenhower "breached a moral code," and had him expelled. This made him an enemy of Eisenhower Holt, which is why Eisenhower is so cold to Amy and Dan.
He was sent to Turkey at the same time as Hope because he had been ordered to make Hope Cahill fall in love with him. However, when he met Hope, he was enchanted by her beauty, intellect, and kindness. He later realized terrifying information about the Vespers and cut his ties to them, even though it would put him in danger for the rest of his life. Before he proposed, Arthur told Hope about his mission, but she already knew, because William McIntyre's spies have been following him for months. When they married, he adopted her last name, Cahill. He later became a mathematics professor in Boston. Together, Arthur and Hope had two children: Amy and Dan Cahill. When the Cahill's house caught on fire, he went back inside to save a poem with one of the clues, but was caught in the fire. Apparently, Arthur has not died, evidence from A Kings Ransom. In A King's Ransom, Dan received a text claiming to be from him. In The Dead Of Night, Dan asked him to prove it by sending him the name he called Dan as a child. He received the answer: Moon face, which was the correct answer. In Shatterproof, Dan receives a text saying that Arthur set them up to succeed at the Pergamon Museum, and that he will explain what the Book of Ingenious Devices is later. But, in Day of Doom, it is revealed that it was Isabel Kabra faking the texts to find out where the serum was.
- Grace Cahill - Mother-in-Law (deceased)
- Nathaniel Hartford - Father-in-Law (deceased)
- Hope Cahill - Wife (deceased)
- Dan Cahill - Son
- Amy Cahill - Daughter
- Shep Trent - Cousin
Dan has a picture of his father. He is described as being tall and tan, with salt-and-pepper hair and a nice smile. Naturally, this is the first book where he is mentioned.
- He was very good with numbers because he is a math professor.
- He had a photographic memory like his son.
- He had a "famous lasagna" that he makes, as said in the Top Secret part of Card 95
He does not appear online.
His main card is Card 246.
- McIntyre once disapproved of his relationship to Hope.
- Shep once said he was a daredevil when they were young.
- He was born on July 29, 1959.
- He was accused of stealing a rare map from the British Library in the August of 1989.
- He was detained by Turkish officers after being caught in the Hagia Sofia after hours of being there.
- He was found unconscious on the Charles Bridge, in Prague, in January 1992. He claimed to have no memory of being attacked.
- His nationalities are American, Canadian and Irish.
- He visited more than 60 countries with his wife, Hope Cahill, including Cambodia.
- He has scholarship at MIT, Stanford and UMASS made in his honour.
- He was under consideration for the Nobel Peace Prize.
- He has a similiar face to Damien Vesper III, if you compare Cards 246 and 427 to Card 312.
- He never was granted official Madrigal Branch status.
- He was loved among his students at MIT for his laid back teaching style
- He did not like to leave Dan at the day care, so he would bring Dan him with him.
- He was an avid collector of ninja items. This might be why Dan likes ninjas and be a collector.