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William James McIntyre was Grace Cahill's and Mark Rosenbloom's lawyer. He is the executor of Grace's will and officially began the hunt for the 39 Clues. He was a Madrigal.


He was born on May 5, 1959. He had a dog named Oliver. He was a former Navy SEAL and was chosen to be Grace's lawyer because she knew him well.


Appearance and Personality[]

William McIntyre was a tall, craggy man. He was bald and had a pointed nose. When remembering him, Amy and Dan Cahill thought of McIntyre as a lovable and sweet man who did his best to give both Cahills a normal life for as long as possible.


The Maze of Bones[]

William first appeared as Grace Cahill's lawyer when speaking with her about her will. He was unsure she should start the hunt but agreed to doing it. He later gave Amy and Dan Cahill, as well as several others, a choice of one Clue or one million dollars. Seven teams were soon formed, and McIntyre made sure to have Amy and Dan heard some eerie advice. Eisenhower Holt and his family later set Grace's mansion up into flames, rendering McIntyre unconscious until he was saved by Amy and Dan. After McIntyre had fully recovered, Amy and Dan were forced to travel to a foreign country, so McIntyre offered to take care of Saladin, the Cahills' pet. While in the lawyer's care, a tracker was placed on Saladin, unbeknownst to Amy and Dan.

One False Note[]


William McIntyre

Saladin started scratched himself around the neck resulting in Nellie Gomez, the Cahills' au pair, taking him to a doctor. After Amy and Dan returned from investigating a place where a possible clue lurked, Nellie showed them the tracking device. Infuriated, Amy and Dan planted the tracking device on Alistair Oh. While near Oh, Amy and Dan found important papers in his cane, and stole them. Oh soon noticed the theft and, upon finding McIntyre, who was following the device, began to scold the lawyer, wrongly suspecting McIntyre had taken the papers he had had in his possession.

The Black Circle[]

William McIntyre was did not appear in this book, but in the Lucian Archives on the Cahill Web, an intercepted letter from William is pictured. It seemed to have taken place after the events Amy and Dan faced in the Amber Room.

From: William McIntyre

To: F

I heard about what happened in the Amber Room. It might give us an advantage if the children trust you rather than fear you. Even after all they’ve witnessed, it is not in Amy and Dan’s nature to think ill of people. It makes them very vulnerable.

The children found those Australian passports Hope and Arthur used. They’re en route to Australia now. I fear what Amy and Dan discover there may turn them from the path we need them to follow. We must do whatever possible to hide the truth about their parents.

I will continue to keep you updated. Please e-mail me so I know that you’re alive, and not rotting away in some Lucian dungeon.

- William

Into the Gauntlet[]

Madrigal Logo

Mr. McIntyre's branch

He was present in a small dark room along with a mysterious associate, Fiske Cahill, nicknamed the "Man in Black" by Amy and Dan. The two listened to every word Amy, Dan, and their au pair exchanged.

He was later found by Isabel Kabra, and tied to a tombstone, though after being rescued, celebrated the news that the hunt for the 39 Clues had finally ended, with Amy and Dan victorious.

The Black Book of Buried Secrets[]

It is revealed that in The Black Book of Buried Secrets, he was responsible for the fake passports and for opening the Visa Gold card that Dan had in the locker in the book The Black Circle.

The Medusa Plot[]

He was at Grace's mansion after an incident where Amy and Dan were forced to fend off three goons. McIntyre reveals to them that 7 Cahills had been kidnapped at the time of the incident, including Nellie and Fiske. McIntyre is later present to briefly explain to Evan Tolliver what "Cahill business" is about.

A King's Ransom[]

He was spoke with Amy and Dan, and provided comfort for them. He later did some research and concluded that Amy and Dan were in more danger than they thought. A staff impostor came into his room at that moment, posing as a waiter. McIntyre recognized him and exclaimed "It's you!" before the impostor plunged a syringe into McIntyre, injecting poison into the man's neck, killing him. In his final moments, McIntyre managed to point a finger toward a piece of paper well-hidden in his shoe. The paper contained a list of locations, including Pompeii, which was mentioned in Grace's notes. Jake Rosenbloom later found out that each location was a subduction zone, where volcanic eruptions and earthquakes occur often. Pompeii was the first test, meaning it was the "first" out of multiple tests. Erasmus Yilmaz found McIntyre, dead in his hotel room. The two were planning to discuss the The Vespers. Yilmaz examined the room, piecing together the situation, and what had happened, until he found the hidden paper on McIntyre. After scanning through it, Yilmaz heard voices in the hall, likely belonging to policemen, resulting in him rushing out after saying goodbye to his old friend.

Nowhere to Run[]


McIntyre had a funeral at this time, however, the funeral was interrupted by Founders Media, because they wanted to find and kill Amy and Dan.



William's birth certificate is shown at Card 137. It was also revealed on the Agent Handbook in the books and below.


  • Mis0-SC2
    The password to McIntyre's Blackberry was "OLIVER", after his dog.
  • He had 6 toes on his right foot, visible on Card 137: William's Heritage.
  • McIntyre preferred being called "Mac."
  • He was allergic to shrimp.
  • McIntyre sent Nellie coded emails under the alias "clashgrrl" 
  • He initially did not approve of Hope's relationship with Arthur, suggesting they strip Hope of her Madrigal status, which Grace did not agree on in Card 334.
  • McIntyre used to have a dog named Oliver.
  • Dan affectionately called him "Mac and Cheese."