Page 35 of The Truth You Told (Raisa Susanto #2)

CHAPTER TWENTY-SIX

Raisa

Now

“Why did he use the Alberti Cipher?” Raisa asked. The prison had stuck them in an interrogation room and warned them that it might be up to an hour before they could pull Conrad to talk to them. There was a schedule to keep on execution day, after all.

“He never said.” Kilkenny was sitting in one of the metal chairs, perfectly still, not fidgeting at all.

“It’s just so simple.” Raisa had her tablet out, and she was studying the letters again like a self-soothing exercise. With writing samples, she at least felt like she could regain a little control of the trajectory of the case. “What would you say Conrad prized in himself? Over everything else?”

“His intelligence,” Kilkenny answered without missing a beat. Then corrected himself. “His supposed intelligence.”

“Right. And he was goading you with it, taunting you—the tone is completely smug throughout,” Raisa said. “His writing is extremely clean and grammatically accurate. He definitely saw himself as smart.”

“But . . . ?”

“The Alberti Cipher is so simple,” Raisa said again. “It’s not complex; it doesn’t take an above-average intelligence to understand it. A computer would have been able to decode it, given more than three days. There’s nothing intellectually elegant about it. So why choose this particular one?”

Kilkenny hummed in thought. “I don’t know. That always seemed to get pushed down on the list of importance.”

Raisa nodded. She got it. Investigations were all about triage, and she wasn’t about to parachute in later and criticize every mistake. But as a linguist, she couldn’t help but be slightly appalled more focus hadn’t been put on the code.

“You all had an expert who worked on deciphering each of them, right?” Raisa asked.

“Yes, he never could make much headway.”

“No, I wouldn’t imagine he could,” Raisa said. The code was a simple one, but not when placed in a block like it had been. There was no way to cheat using short words and letters that often coupled up together. “Did he have any thoughts about the Alberti Cipher?”

“I don’t remember in particular,” Kilkenny admitted. “But I would think that means he didn’t. Nothing groundbreaking at least.”

Raisa nodded again, still staring at one of the letters from Conrad.

There was a crack in the foundation, she knew there was. And it was something she could exploit to bring the whole house down.

She just couldn’t see it yet.

Years ago, she’d watched a movie about Alan Turing, the man who’d broken the Nazis’ Enigma code—which had seemed impossible until it had been done. In one of the more cinematic moments, Turing was listening to two radio operators talk about how they recognized a particular enemy radio operator by the call signal he used—it was supposed to be random letters, but instead he used the name of his girlfriend. Turing realized that if they could isolate two or three words in a message they knew was coming every day, their primitive computer could use pattern recognition to decode the rest.

They realized the Nazis sent a weather report at 6:00 a.m. every morning and signed off Heil Hitler .

Raisa closed her eyes.

With both codes, a handful of letters of gibberish kicked off each message, but then, without fail, they started the same way.

With Conrad, it was My dear Agent Kilkenny —or some other overblown salutation.

With their impostor, it was Dear Callum .

It was one of the first things she’d noticed about the different idiolects.

She’d thought it was their impostor making a mistake—or not even trying to mimic Conrad’s voice.

What if it served a different purpose, though?

Why me? Kilkenny had asked.

Why you? Conrad had taunted in one of those letters.

She stood and crossed to the door in three jerky strides. When the guard answered her knock, she asked, “Do you guys have a portable whiteboard I could borrow?”

The guard gave her a blank stare. “Um?”

“Shit,” Raisa murmured, and swung back to Kilkenny. “This is why a linguist was never a waste of resources. Text me if Conrad’s schedule frees up.”

“Wait, what are you—” Kilkenny called after her, but the rest of the question was cut off by the door.

Raisa didn’t slow, still clutching her tablet, where she had copies of both the encrypted and decrypted letters.

The guard helped her find the library, which had a room with a standing whiteboard. Raisa briefly considered pushing it back through the hallways to the interrogation room with Kilkenny, but the sheer absurdity of that image stopped her.

Instead, she grabbed a marker and pulled up one of Conrad’s letters.

He hadn’t wanted the investigation team to actually decrypt them before the victim was dumped. He wasn’t stupid or sloppy. The whole shtick of including the name was just a power play from a sadistic asshole. But it could only be a power play if he came out on top every time.

Again, he was intelligent, or intelligent enough to try to think through any dumb mistakes that he could make. Using Kilkenny’s name—even when throwing in some extraneous letters in there to fool the computer—was, in theory, a dumb mistake.

Somewhere in the first line, there was a double letter that would always equal k , and a double letter that would always equal n . Once those two pairs were pinpointed, they could figure out a handful of other important letters, certainly enough to at least partially decrypt the message.

If he’d really wanted to make sure his code was rock solid, he would have changed that up.

Which meant he’d used it for a purpose.

Raisa laughed in disbelief. It was so simple and so stupid and yet it had worked.

Why you? Conrad had taunted. Maybe it was partly because of Shay.

But it was partly because Callum Kilkenny had enough repeating letters to establish a fucking pattern, one that would show up in every single letter.

The only reason to take that risk, though, was to make sure the letter was decipherable to someone .

Raisa’s butt hit one of the seats as the realization slammed into her like a blow.

Their two killers had been talking to each other.

Raisa breathed out a curse, let herself just stare for a minute, and then went to work.

The message to the impostor wouldn’t have been an Alberti Cipher—it would have been hidden beneath that cipher.

She ran through the list of codes she knew. She discarded a few based on simplicity or complexity, and landed on the Vigenère cipher. It was a close cousin to the Alberti, but it was more elegant and harder to crack. It also required a key word for it to work.

It checked enough boxes to be worth trying.

The first step required creating a table on the whiteboard full of Caesar ciphers. Those were notoriously some of the easier codes to crack—all they did was shift the alphabet down a letter instead of jumbling it. Where it got complicated was when you created a grid of them.

To do that, she wrote the alphabet across the top of the whiteboard and then vertically down the side as well. On the second horizontal line, she started the alphabet with the letter B and wrote out all the letters until they wrapped around to end with A getting paired with Z . With just those two lines, she had the simplest Caesar’s cipher—here, each letter of the alphabet was shifted one spot.

KING became L - J - O - H .

She repeated the process all the way down her vertical line of the alphabet, each horizontal line shifting the alphabet one letter from the one above it.

Once she had her twenty-six lines, she had something to work off.

Then came the harder part—the key word.

If the two killers were communicating via publicly printed letters, it was safe to assume the key word would be in the message itself—something both of them could easily identify but would slip under the radar of the task force.

The name of the victim, of course, was an option—Raisa tried it both coded and uncoded.

Nothing but gibberish came up.

She chewed on the marker as she stared at the table she’d drawn.

The salutations. They were the only things about the messages that always remained the same. And in both, no matter how many letters they threw in front of the salutations as gibberish, they were still easy to find.

Which meant the easy letters to isolate for a key word would be the gibberish that came ahead of the salutations.

Sneaky bastards.

She picked a message at random, and wrote the five letters that preceded the salutation on the board next to her table of Caesar ciphers.

Raisa exhaled. The task was daunting. To manually crack a Vigenère cipher, she would have to write the five letters from the key word over each letter in the Alberti-encoded message.

When that was done, she had a message full of matching pairs: R and D , then F and T , and so on. That gave her two coordinates on her Caesar grid—where those two letters intersected in her twenty-six rows of alphabets was the letter it actually represented.

The process took her forty-five minutes to go through the shortest message, and she kept having to pull herself out of her near-fugue state to check her phone. No text came in from Kilkenny.

When she was done with the cipher, she stepped back from the whiteboard.

B ETTER LUCK NEXT TIME

The knock on the door startled her into dropping the marker.

“Jesus,” she breathed out as Pierce poked his head into the room.

He was about to say something but then caught sight of the board. “What’s this?”

She didn’t actually think Pierce was their impostor-and/or-vigilante. But it still made her pause, made her study him closely for panic or fear.

There was nothing on his face other than curiosity, though.

“I figured out a hidden message within Conrad’s letters.”

“Holy shit.” He stepped fully into the room. He stared at her scrawled words, at the Caesar cipher table, at the crossed-out letters for a long time. “How did you figure this out?”

“Too long to explain,” Raisa said, waving away the fact that she might have gotten the idea from a Benedict Cumberbatch movie. No one needed to know that part. “But I think our second killer and Conrad were talking to each other through these messages.”

Pierce squinted at the board. “Can you figure out the other ones?”

“It would take a while,” Raisa admitted, and waved at her work. “This took over an hour.”

“Would a computer be able to do it, if it knew what to look for?” Pierce asked.

“Maybe,” Raisa said. She wasn’t the most technologically savvy but ... she knew someone who was. Delaney had said she would continue to help, if possible. “I can send them to someone who probably has a program to run them through.”

“They’re approved?” Pierce asked.

Technically . . . “Yup.”

“Let’s do it,” he said.

“Did you need me for something else?” she asked.

“We got an address for Max Baker,” Pierce said. “It’s about an hour away, and I’m going to drive out now. I know Kilkenny is waiting on Conrad, but I wanted to see if you wanted to ride along.”

It would probably be a fruitful interview. Max was their missing component, the person who kept coming up time and again in their case.

Perhaps even playing vigilante—which given the hidden message Raisa had just cracked, seemed a more likely scenario than some of their other wild theories. She bet if she lined up the dates, she’d find this letter was close to the time one of the male victims had been killed.

But Raisa didn’t shine in interviews. She knew where her strengths lay, and they were here, in this room, with a whiteboard and a bunch of letters.

She shook her head. “I’m going to keep working this angle.”

“Okay, keep us all updated,” Pierce said.

Raisa nodded, gnawing on the inside of her cheek as she debated asking. In any other situation, she wouldn’t have pushed, but this was execution day. And if they were going to come up with anything to blindside Conrad with, they couldn’t be squeamish.

“Did you not like Shay?” Raisa asked. It was mostly a shot in the dark. But for some reason when she pictured the Christmas party Kilkenny mentioned, it wasn’t Pierce hitting on Shay. It was him warning her off Kilkenny.

Pierce stopped, his back to her, the line of his shoulders tight. “Why would you ask that?”

Which sounded like a nonanswer, but really was one. Because if he’d liked her, he wouldn’t have hesitated to say so.

“Just something else Kilkenny mentioned,” Raisa said. “About a Christmas party.”

She had expected that to ratchet up the tension in the room, but instead he relaxed. It was barely noticeable, but she could tell he’d been braced for something else. He shifted so that she could see his face once more.

“I remember that,” he said. “It was nothing. It was our fourth year hunting Conrad, and I got a little weird with the women in my life. Started handing out Mace and enrolling them in defense classes. I probably came on a little strong, though.”

“Yeah, I get that,” Raisa said. But why had he been expecting a different question? Why had he been worried about it?

He stared at her, but she just sent him a smile.

The one he gave her in return was flat and forced. Then he turned and left.

She understood why Kilkenny had argued that Pierce wasn’t their second killer. The reasoning was compelling enough that Raisa hadn’t felt in danger just then.

Pierce was hiding something to do with Shay, though.

And Raisa hoped that if they figured it out, it wouldn’t be the thing that made Kilkenny realize he could, in fact, be hurt again.