The Clandestine Countess by Judith Lynne

Five years of silence.
Seeing Bess again is a kick in what’s left of Dan’s soul. She makes a fine ballerina. And actress. And thief. She can be anything… except his.
If he can catch one more criminal, he can buy her the life she deserves. She’ll finally be safe, and that’s all he ever wanted.

Five years alone.
Bess decided long ago her scowling, black-haired boy from London’s gutters must be dead. Now he’s back. With no explanation. She ought to kill him herself.
But she fills the void he left by collecting titled admirers. Including one lord in particular who praises all her skills… even the ones that break the law.
When Bess finds out her night-time escapades have dropped her in deep, deep trouble, she’ll have to pull both herself and Dan out of a pit of intrigue with consequences far beyond London.

Their only chance is to remember how to rescue each other.