She Slips Away by Georgia Wagner

Artemis has her life back, but she needs to lay low for a while. She retreats to a sleepy beachside resort for some much needed R&R.

But then two teenagers go missing. According to security, though, they never left their rooms. Now, Artemis is reluctantly dragged back into a game of cat and mouse in an old castle-turned-hotel. Amidst the ancient, imported stone work, and the luxurious resort amenities, she hunts a killer who strikes without a trace.

At the same time, she's still in contact with her family of fugitives. She knows it isn't advised, but Artemis considers bringing in her own father to help on this most baffling case.