I love all five Fire & Frost stories, but this is my favourite.

When a lovely—but foolish— young woman marches into an insalubrious alley full of homeless former soldiers, Ethan Alcott feels something he thought dead stir to life: his sense of honor and will to live. Her innocent efforts to ease the suffering of men might have touched his heart if she hadn’t put herself in danger to do it. Someone needs to take her in hand.

Lady Flora Landrum chafes under her brother’s restrictions, but she’s willing to compromise if they can join forces to join in the Duchess of Haverford’s charity efforts. When she discovers that the mysterious one-armed ruffian she encountered in a back alley is Lord Ethan Alcott, son of the Marquess of Welbrook, her astonishment gives way to determination to make the man see reason.

Courage takes many forms. As Ethan comes to admire Flora’s, perhaps he can recover his own.

And here’s an excerpt:

Flo heaved a sigh of exasperation and closed the distance between them, grabbing his shoulders, and meeting his lips with her impatient ones. After a heartbeat he returned the kiss with an achingly tender one, using his damaged arm to pull her close while he feathered his graceful fingers across her cheek.
“Much better,” she sighed against his neck, “But know this. I can wait out my mourning and your illness, but do not ask me to be patient.” She spat each of the last words out one by one. “I am not a patient woman when I know what I want, Ethan Alcott, and I want you.”
He kissed her again, this time deeply, passionately, possessively. When she moaned and pulled him closer, he pulled back, tipping his forehead onto hers. “Your brother believes you deserve a Season. I agree. If you still want this in a year…”
“God save me from men and their honor,” she muttered into his cravat. “I’m not promising an entire year. My time of mourning ends September third. I expect to see you at Chadbourn Park that very day.” She grabbed his lapels and gave him a shake.
“I will court you properly,” he swore.
She rolled her eyes. “If you insist, you may make it a courtship, but Ethan, don’t be too proper.” Then she kissed him again, and he forgot to reply.

Meet Flo:

“War is an ugly thing. It demands inhuman amounts of courage, and can be soul destroying.”
“You mean they may have turned coward? They bring shame home with them?” Flo asked, trying to think it through.
“Sometimes, yes. But war can strip off the veneer of civilization. Men are driven to savagery of which they didn’t know themselves capable.”
“But not all of them surely, and the war is necessary, is it not?” Flo asked. “The Corsican is a beast, and if they don’t defend us what will happen?”
“Necessary, perhaps, but the longer it goes on the more it eats at them. They see and do things they can’t talk about at home—both on the battlefield and off.”
Flo mulled that thought over for a while. Her companion’s sympathetic voice interrupted her reverie. “We’re not meant to know, and they’re not to be condemned by those of us who weren’t there.”
“No, I suspect not. Who knows what we would do in that situation? The women of Spain have suffered greatly,” Flo murmured. The papers spoke of hunger and disruption, but she could guess what undefended women on their own might face.
Lady Georgiana nodded gravely. “We can only care for them, while they heal.”
“Shame would be a terrible burden, would it not?” Flo remarked, not requiring an answer. The image of Ethan Alcott’s deeply sorrowful eyes came to her.
What had those eyes witnessed? Things he dreads his family knowing, I’ll wager.
Another thought came to her. Her sister never spoke to Flo about her marriage. Flo assumed it to be fear; now she wondered if it was shame, an even more debilitating emotion. Shame festers when hidden, she thought, and it brought Ethan Alcott to mind again.
How will we help him heal? she wondered. It didn’t occur to her to question the determination that she and Will between them would try to do just that.

And Ethan:

The cold had stiffened Ethan’s bones and numbed his injured stump until he thought he likely could not rise even if he wanted to—even if he had somewhere to go. He knew he should move lest the cold take his worthless life, but the ice around his heart seemed to have frozen all motivation as well.
Odd, he thought idly, that the cold of Mayfair could kill a man as thoroughly as the icy streets of the east end. His father’s garden smelled better, however, even with the flowers dead and the hedges withered and brown. His feet had found the garden with no conscious decision on his part after an hour or more of aimless wandering in the dark streets of London on the coldest night in Ethan’s memory. Now he hunkered between the cold stone of the garden shed and the unforgiving wall, unable to move.
The early morning sun rose weak and grey, but enough to pierce the fog and illuminate the place as if through a veil, and memory seized him. From his haven between the two walls he could see the edge of a stone bench, one he and Edmund used as a pirate ship or galloping steed as the mood seized them in boyhood. One of the balconies two stories up would open to his brother’s room, the other to what once was his. Memory left him with a hollow longing.
He had left Chadbourn’s rooms in a panic, thinking to get as far away from the overbearing Landrums as possible. They pushed him, brother and sister, to open his soul to his family, something he could never do. It would hurt them too badly. Yet, here he was. Perhaps the warmth and obvious affection of the Landrum family made him sentimental. Perhaps he’d allowed Lady Flora’s earnest plea—and her gentle gaze—to penetrate the protective shell he inhabited.
He tossed about for somewhere to go—anywhere but here—but found none. He knew he ought to return to the Albany, but he found it harder and harder to think clearly. Before he could make the effort to rise, the back door of the elegant townhouse flew open and a flash of blue pushed past two men and down the steps.
His heart stuttered at the sight of Lady Flora Landrum turning her head from side to side, searching the garden until she jarred her coiffure loose and one chestnut lock tumbled over her ear. A spark of warmth curled itself around his heart. The foolish chit. She’ll catch her death without a cloak.