Welcome to Baker Street

9. Sibling troubles

The unexpected announcement leaves Sherlock in shock: he doesn't stir an eyelash, he barely breathes.

Anderson intervenes to explain the situation scientifically.

"As far as we can get from lab results, it's a case of monozygotic twins, which are genetically nearly identical. The DNA is very similar with just slight differences only detectable through the analysis of single-nucleotide polymorphism. But the police rarely run such an examination or dig that deep, which is why we initially thought it was good enough for a match. Identical twins, however, do not have the same fingerprints. The contact with different parts of the environment inside the womb produces slight variations in the same digital, making them unique."

He pauses to let Holmes grasp the concept, then adds, "I think this is all the medical knowledge you might need to believe that we aren't lying."

Sherlock takes a deep breath and protests, "It's never twins."

Lestrade shrugs. "Apparently, this time it is."

"How can there be no record of it? Nobody could hide such crucial informati-" he stops talking mid-word, while a distinct scene comes back to his mind. He shuts his eyes close, and inside his mind he sees his brother standing in his living room, trying to hide anguish and concern. He relives their conversation through his memory as the words they exchanged echo in his mind.

/

"I'm here to give you a case..."

"National importance?"

"International."

/

Sherlock comes abruptly back to reality as a sudden realisation strikes him. He mutters, "Wait, what poison?"

Lestrade lifts a puzzled look at him. "'Scuse me?"

"What was the poison that killed her? Give me the lab results," he yells at the two policemen in the room, and Anderson disappears into the adjacent room, re-emerging a second later with a folder in his hands. He hands it to Sherlock without a word.

The detective skims the report searching for a particular substance in the victim's bloodstream, then he tilts his head backwards and closes his eyes, murmuring, "Mycroft."

The inspector scowls when he catches that name.

"What does your brother have to do with this suicide?"

"I have to go." Sherlock tosses the folder at him and rushes down the stairs. He takes his phone and makes a call while marching hastily down the street.

"I'm busy, dear brother. Try to call me on another day. Or another life," sighs an irritated voice on the other end of the line.

"Mycroft, I think I've just run up against the case you wanted to give me earlier," the younger Holmes urges him.

"I can't speak now, Sherlock."

The detective keeps pressing him, "I need more information about them. I need to know where she—"

"I said I can't speak, for God's sake," Mycroft interrupts him. "We've just found a mole in our system. I can't speak on the phone; I can't communicate through telegrams or letters, and I certainly cannot meet you in person right now. Everything is compromised, and I must sort it out. You are on your own. Do whatever it takes, but hurry. We are running out of time," he pronounces cryptically and hangs up right away.

"No, Sherlock, wait." Lestrade has followed him in the street and runs to him in time to enjoy the puzzled expression on his face at the end of the call.

"You can't go now. We've barely even started."

Holmes raises an arm to hail a cab and turns to him to reply, "I'm done here. There's nothing of any importance."

"A woman lies dead inside that flat and her twin sister is missing," Lestrade objects stubbornly.

Sherlock shoots him a withering look. "I can assure you the worst is yet to come."