Sins of the Father by K. Sterling

It turns out there may be something that Mr. Lavender can’t kill. A secret is coming to haunt Lake Cliff and the people Lavender holds dear are in grave danger. Time is just about up, and the careful web of lies and bargains he’s woven is unraveling.
As if things aren’t tense enough, Lavender has a very serious complication: Agent Paul Sloan. He’s on the trail of a sophisticated serial killer who’s pretending to be Mr. Lavender. Paul is determined to discover who’s copying our favorite assassin, and why. Most importantly, he wants to know why Lavender doesn’t mind that someone’s stealing his secrets and flaunting it.
How do you make a killer and what happens if the copy is better than the original? Something vicious and twisted has come to play and Mr. Lavender can’t keep it off his doorstep any longer. Whether he likes it or not, Lavender has to rely on the help of Dr. Aiden Sharp and company to stop a monster before it’s too late and evil arrives in Lake Cliff.
Welcome back to Lake Cliff; one of the most dangerous places you’ll ever call home.