[Western Crossover] A Detective, but in His Childhood

Also titled: "When You Say You're the Greatest Detective, You'd Better Mean Poirot"

Hermine Poirot's greatest wish in life is to follow in her uncle's footsteps and become the greatest detective in the world.

And detectives usually have a friend for an assistant, right?

“I will inherit the name of Detective Poirot, solve every mystery, identify every culprit, and become the world's greatest detective. And you, my friend, will be my Doctor Hastings.”

After finishing her tiramisu in a wardrobe, five-year-old Hermine solemnly made this promise to the little boy outside it.

Bruce Wayne: “...All right, so can you come out now?”

When he was five, Bruce Wayne found a strange little girl in the attic wardrobe, sneaking a piece of cake.

The girl said she was going to be the world's greatest detective, and ordered him to provide a tiramisu, a cup of Earl Grey tea, and a cookie. That way, he would “just barely be lucky enough to become Assistant to Detective Poirot.”

Bruce: ...?

Little Bruce didn't understand, but he did as he was told.

And so he gained a little friend.

They went on adventures in different worlds, until they both became recognized as a detective team.

A long, long time later, Bruce Wayne returned to Gotham and became Batman.

Hermine Poirot dropped by one day and gave him a thumbs-up, pleased. “I knew you were my loyal assistant... Wait! Why are people calling you the greatest detective?!”

Bruce: :)

When Hermine was five, a neurotic man in a suit and Converse barged into her home and shrieked as he hugged her aunt, Donna Noble.

Her aunt said the man was called the Doctor, the most troublesome, arrogant, crybabyish, and powerful... alien in the universe.

Hermine: (blank stare)

Her aunt also said that she had once traveled through time with the Doctor in a police-box-shaped ship to save the world, earning the title Doctor Donna.

Hermine: (blank stare)

Her aunt went on to say it was no big deal. They had only saved a family in Pompeii, freed an enslaved alien race, gained Time Lord powers, and saved Earth from destruction countless times along the way.

Hermine: ...???

Hadn't her aunt said she was the most ordinary British woman on Earth?!

Hermine hid in the wardrobe to think about her life. The next second, she opened the door and found herself in a strange world, with a little boy standing blankly in front of her.

Excellent. Detectives always have an assistant and partner, and the Doctor always has a companion. So she, Hermine Poirot, solemnly declared once again that, as a future great detective, she would choose this boy named Bruce Wayne to be her deputy!

Hermine's wardrobe became a second TARDIS. During school breaks, she and Bruce traveled through countless worlds, solving all sorts of cases until they became famous detectives around the world.

As an adult, Hermine decided to take a graduation trip.

Her secondhand pickup truck broke down in Gotham.

She got out, inspected it, and found tampering. A prank.

Hermine spun around and pinned her good partner, who had played the prank and was about to give her an enthusiastic hug. She shouted, “Who's trying to hurt me?”

Bruce: “...Me?”

Hermine: “...Huh?”

As a detective, you will handle the following cases:

1. A calf theft in the Shire village of Hobbiton. Hermine shouts, “Don't worry, I'm a detective. I'll take care of everything!” The hobbits politely ask, perplexed, “What's a detective?”

2. A child-trafficking case in London. Hermine and Bruce carefully study the case, then realize inside the warehouse where the abducted children are held, “Oh, we've been captured too.”

3. A haunting in Kansas. They run into the demon-hunting brothers and earnestly learn their trade in case it's ever needed. Later, when they run into Crowley, Hermine and Bruce each grab a salt shaker and spray the demon with salt.

4. We're fifteen! Time to challenge Sherlock Holmes! @%#*?!# Why have we been arrested for murder first?!

5. ...

Reading Guide:

1. Heterosexual romance, pairing with Bruce Wayne. The story starts with two five-year-olds chattering as they travel around the world and become detectives. They grow up later.

2. A crossover identity setup. The heroine is the niece of Donna Noble from Doctor Who, raised by her aunt and with a personality like hers. Rose, Donna's daughter in the 60th anniversary special, won't appear for now. The story also crosses over with Agatha Christie's universe. The worlds overlap and time folds in on itself, so Hercule Poirot is Hermine's uncle by blood.

3. A lighthearted, multiverse detective story. Gotham isn't the main setting. Thomas and Martha won't die, but Bruce will still become Batman.

4. There are quite a few crossovers: Middle-earth, Doctor Who, Supernatural, Good Omens, Sherlock Holmes, Miss Marple, and many more.

5. Although Poirot is Belgian, Hermine is British.

6. There will be cases of all sizes, from a calf stolen in a neighboring village to murder. Anything might show up.

7. Maybe it'll be a short story, maybe a long one. Here's a blurb for now.

Blurb written on 2026.1.29

Theme: Home is behind us, and the world is just ahead.