Sophia Holmes and the Blind Banker (Sherlock's Daughter Fanfic) *Completed*

Chapter Four

In the taxi, dad hands me the book and I flick through it, seeing the date stamped in the front. This can tell us a lot: the book belongs to the West Kensington Library and is dated for the day he died. Was he at the library when he was threatened?

We stride through the double doors at the front of the modern building, and onto an escalator which takes us up to the aisle, the book is from.

I know this library like the back of my hand, as it's often the building of choice for me to go to when I think, so I have no trouble leading dad and John to the right place.

"Date stamped on the book is the same day that he died," dad states, for John's benefit. He checks the reference number stuck to the bottom of the spine, then wanders down the shelves, taking out books and examining them. I look further down, whilst John starts pulling some out opposite dad.

"Sherlock," John says, and I spin around to look at the space where the books were. Another tag sprayed in the same paint as before fills the gap.

Seeing this, dad steps forward, and takes a handful of books in each hand, revealing another identical set of graffiti to the one in Sir William's office. Instinctively, I reach for my phone and snap two or three pictures each of the new graffiti, then jog to catch up with dad as he turns on his heel.

Dad hails another taxi and we sit in silence, our thoughts churning over in our minds. John looks idly out of the window as we work. Two sets of graffiti, both exactly the same, but what's the link? The murderer needed to send the same message - a threat - to two people, but why?

I step out of the cab first and sprint up the stairs to the printer, printing off the new photos and sticking them above the others on the mirror, leaving just a small gap in the centre of the mirror. Dad and John join me by the fireplace, and together, we stare at the images.

"So, the killer goes to the bank, leaves a threatening cypher for Van Coon; Van Coon panics, returns to his apartment, locks himself in," dad recites, using the information we have to piece together the china fragments. "Hours later, he dies."

"The killer finds Lukis at the library; he writes the cypher on the shelf where he knows it'll be seen; Lukis goes home," John continues.

"Late that night, he dies too," I add.

"Why did they die, Sherlock?" John asks softly.

Dad traces his fingers over the line painted over Sir William's eyes. "Only the cypher can tell us," dad says, tapping his finger against the photo. We need some advice from an expert to tell us more. Dad's expression sharpens as he too reaches the same conclusion. "Come on John," he says brightly, standing up and striding towards the door.

"Hmm?" John murmurs, following us.

I tap a small message into my phone, send it, and receive one straight back. Smiling, I step into the cab dad hailed before my arrival and feed the cabbie the address.

***

We walk across the centre of Trafalgar Square towards the National Gallery, trying to ignore the funny looks we're getting. Obviously, John's blog is picking up on followers, and more people are recognising who we are.

"The world's run on codes and cyphers, John," dad states randomly. "From the million-pound security system at the bank, to the PIN machine you took exception to, cryptography inhabits our every waking moment."

"Yes," John says sarcastically, "okay, but ..."

"... but it's all computer-generated: electronic codes, electronic ciphering methods. This is different. It's an ancient device. Modern code-breaking methods won't unravel it."