It's in His Kiss (Bridgertons 7)

“I’m not going to boost you up,” Hyacinth said impatiently. “So unless you’ve a crate hidden away somewhere, or perhaps a small ladder—”

“Just go,” Gareth practically growled, making a step for her with his hands. He had done this before, plenty of times. But it was a far different thing with Hyacinth Bridgerton brushing alongside his body than one of his school-chums.

“Can you reach?” he asked, hoisting her up.

“Mmm-hmm,” was the reply.

Gareth looked up. Right at her bottom. He decided to enjoy the view as long as she had no idea she was providing it.

“I just need to get my fingers under the edge,” she whispered.

“Go right ahead,” he said, smiling for the first time all night.

She twisted immediately around. “Why do you suddenly sound so equable?” she asked suspiciously.

“Just appreciating your usefulness.”

“I—” She pursed her lips together. “Do you know, I don’t think I trust you.”

“Absolutely you shouldn’t,” he agreed.

He watched as she jiggled the window, then slid it up and open.

“Did it!” she said, sounding triumphant even through her whisper.

He gave her an appreciative nod. She was fairly insufferable, but it seemed only fair to give credit where credit was due. “I’m going to push you up,” he said. “You should be able to—”

But she was already in. Gareth couldn’t help but stand back in admiration. Hyacinth Bridgerton was clearly a born athlete.

Either that or a cat burglar.

Her face appeared in the open window. “I don’t think anyone heard,” she whispered. “Can you get up by yourself?”

He nodded. “As long as the window is already open, it’s no trouble.” He’d done this before, several times, when he’d been a schoolboy, home on holiday. The exterior wall was made of stone, and there were a few rough spots, with outcroppings just long enough to wedge his foot. Add that to the one knobby bit he could grasp with his hand…

He was inside in under twenty seconds.

“I’m impressed,” Hyacinth said, peering back out the window.

“You’re impressed by strange things,” he said, brushing himself off.

“Anyone can bring flowers,” she said with a shrug.

“Are you saying all a man needs to do to win your heart is scale a building?”

She looked back out the window. “Well, he’d have to do a bit more than this. Two stories, at the very least.”

He shook his head, but he couldn’t help but smile. “You said that the diary mentioned a room decorated in shades of green?”

She nodded. “I wasn’t entirely certain of the meaning. It could have been a drawing room. Or maybe a study. But she did mention a small, round window.”

“The baroness’s office,” he decided. “It’s on the second floor, right off the bedroom.”

“Of course!” She was whispering, but her excitement still rang through. “That would make perfect sense. Especially if she wanted to keep it from her husband. She wrote that he never visited her rooms.”

“We’ll go up the main stairs,” Gareth said quietly. “We’ll be less likely to be heard. The back ones are too close to the servants’ quarters.”