The bright light of day burst through the curtains as Maura opened her eyes.
Turning sideways, squinting at the headache quickly building behind her temple, she realised where she was.
Sitting up sharply, Maura pulled the sheets up to cover her bare chest.
"You know, it's probably a bit late for that".
Harriet's voice cracked as she spoke, her hand resting on her head. Clearly, she was experiencing the same pain.
Maura leaned back into the headboard and closed her eyes.
"I hate gin."
A hand quickly found hers below the duvet and squeezed comfortingly. "Me too."
Almost as soon as it had happened, the contact was gone. Harriet turned her body away from Maura and slowly sat up, revealing the smooth, uninterrupted skin of her back. Reaching down, she picked up a t-shirt and threw it on before pulling a pair of black panties out of her drawer.
"Coffee?"
With her hand blindly searching the bedside table for her glasses, Maura nodded.
Taking advantage of having a quiet moment to herself, Maura stretched and tried her best to process what was happening.
She felt guilty. Guilty, not for betraying Jane, but for taking advantage of a woman who was dealing with her own grief. A woman she was here to support as a friend. Jane wasn't important in this situation- Maura was sure the woman never spared a thought for her best friend after a night with Agent Davies.
It wasn't her problem.
This was between Maura and Harriet.
Harriet was already sat, coffee in hand, at the table when Maura appeared downstairs. Smiling as she walked into the room, Harriet lowered the papers she was reading and offered her friend a seat.
"It's fresh" she said, gesturing to the pot of coffee sat between them.
Maura took a sip and savoured the taste. A good cup of coffee was her favourite medicine.
"Maura". She looked up from her cup, meeting Harriet's gaze. "I think we need to speak to Dr Kaplowitz today. He'll be able to help us."
Maura nodded and went back to her coffee. Obviously Harriet was happy to ignore the elephant in the room for now.
The two women continued to dance around the subject of their evening activities as they walked into the city. Maura hadn't seen much of central Oxford since she had arrived, and she was looking forward to spending a couple of hours traipsing around the city's hallowed colleges and university buildings after their meeting.
Harriet explained that Dr Kaplowitz had been a relatively recent placement at the university. His research focussed on the history of mathematics, specifically ciphers and codes, and Rachel had spent a lot of time in his company.
Victoria College was set back from the road, behind a high stone wall. Dr Kaplowitz was waiting for them in the doorway when they arrived.
"Ladies". Dr Kaplowitz kissed their hands, his charismatic smile causing both women to blush slightly. "Please, follow me."
The professor led them down a long corridor filled with portraits and what looked to be expensive ornaments and statues. "I'm sorry about the clutter" he said as they walked. "When any other college is being renovated, we become the dumping ground. And because we only take postgraduate students, the groundsmen seem to be under the impression that we have the extra space."
The older man shook his head as he turned the corner, reaching for a key from his breast pocket. The office door clicked open and the professor gestured for the women to enter. "Take a seat. Can I get you anything to drink?"
Maura shook her head. "No thank you, professor. I'm fine." Harriet agreed.
"So. Rachel."
Elias Kaplowitz pulled an antique chair over from the corner of the room and sat down opposite the two women. "I must say, her death came as an awful shock. That poor woman had been through so much."
"I'm sorry… what do you mean by that?" Maura questioned.
"Well, Rachel lost a dear friend from Bletchley a few months ago. An older fellow, I believe. No idea of his name, though. She was the one who found him. Dead."
Maura glanced at Harriet, who looked as shocked as she was.
"She never said…" Harriet began.
"No. I doubt she would have said anything, my dear. She was quite shaken. Still, her work was what mattered to her and I suppose that is why you are here."
Maura nodded. "Yes. We… well, I'm a medical doctor and Harriet is a historian, but neither of us have ever spent any time with codes or ciphers. It's all quite new."
The professor leaned back in his chair, his hands resting in his lap. "Where to start? Well, codes and ciphers are two very different things. A code is used for storage. It's a way of mapping one thing onto something else. Usually by shortening it. A cipher, however, is a translation. A cipher's purpose is security.
Rachel's Bletchley work wasn't particularly about either. She was focussed on the people who worked there, but she found an interest in ciphers. Not so much the enigma machine or the Lorenz, but old-fashioned secret messages. Pen and paper stuff."
Maura leaned in, listening intently.
"She didn't have much time for the machine ciphers, really. That was what she used me for- it's my area of expertise and she knew I would provide her with the information she needed to move her own ideas forward."
"Professor, what kind of methods was Rachel able to use?"
Elias' eyes flicked towards Maura, the deep crow's feet exaggerating the intensity of his stare. Noting the subtle shift in her body language, he quickly relaxed.
"Basic stuff. Caesar boxes. Substitution ciphers. Key words. It was just fun and games."
Maura caught Harriet's eye, hoping that a pointed look was enough to get her friend to make the excuses they needed to leave.
"Well, if that's the case I think we'll leave you to your work."
Dr Kaplowitz stood as the two women rose from their seats. "If you have any questions, please feel free to email me."
As they walked out of the college and onto the main road, Maura spoke. "We need to find a coffee shop or something. I have an idea."
"Follow me".
Harriet led them down a meandering side street, one side of the pavement completely full with bicycles. Rather than slow down to allow the slew of tourists to pass them, Harriet grabbed Maura's hand and pulled her into the road.
They didn't let go of one another's hands until they reached the door of the café. "You get a table" Harriet suggested, sensing Maura's desperation to begin working on her idea. "Coffee?" Maura nodded and walked to the back of the room, finding a quiet corner table and pulling out a pen.
Quickly, she wrote the alphabet in large lower-case letters across one of the café's napkins. Harriet placed a steaming cup in front of her and sat down.
"What's up?" She asked, sensing Maura was stalling. "What do you need?"
Maura shook her head. "A key word. What would Rachel have used?"
Harriet leaned back in her chair. "Well, I don't know of any pets. And I don't think her ex-boyfriend is a likely candidate." Maura scribbled their nine-letter code in the corner of the napkin, circling it heavily in frustration.
"Tell me again what the note said."
"I told you. My name and that" she pointed to the code. "Nothing else."
Quickly, Maura began to work out their new alphabet as Harriet sat and watched in amazement.
Sensing she had an audience, Maura explained as she wrote. "It's a simple substitution. Elias mentioned it and it made perfect sense. All you do is replace the first letters of the alphabet with a key word or phrase, using each letter only once, and then substitute in the letters you haven't used."
Maura turned the napkin to her friend, who glanced with confusion at her scribbled handwriting. "Your name was her key."
Underneath the usual ABC, the next line read:
Z
"So then all we have to do is pick out the letters of our code, and see what it said originally."
Harried sat back in admiration as Maura quickly found each of the nine letters and scribbled down its counterpart.
DEPRUPGUQ
MERCURIUS
"Well, it's kind of a word" Harriet surmised. "What does it mean?"
Maura shrugged. "That's what we need to find out."