Four Calling Birds by Emily E K Murdoch

It’s 1817, and Lucy always knows who will answer her call…

Lucy Fitzroy has always had one friend to rely on: Lord Percy Ardingley. Childhood friends with a unique call to encourage the other to venture out into London—and mischief—there’s nothing Lucy likes better than time with him. But for some reason, this Christmas, Percy is…different. Strange. Trying to speak to her about things she doesn’t understand.
He’s back after a few months in the country, and though Percy doesn’t look any different, something has definitely altered between the two of them. If only Lucy could keep her heart rate still for five minutes around him and understand what this strange lurch in her stomach means…
Four calling birds may have been his pet name for Lucy and three of her sisters, but it’s just her and Percy now, and she’s not sure what her friend is calling her to do.
Just when she thinks she understands him, Lucy may find that the call of her heart is stronger than the call of her mind—and the call of the bedchamber may be even stronger still…