GUARD DUTY (4) by Sharon Dunn: Rookie K-9 officer Valerie Salgado witnessed a murder. A crime syndicate is now after her, since she would recognize the killer, a woman known only as the Serpent. FBI Agent Trevor Lewis needs Valerie’s help to apprehend a fugitive, but he is leery of working with a rookie, as he feels responsible for his own rookie partner’s death. But as the threats against Valerie increase, Trevor is determined to protect her. Part of the Texas K-9 Unit series, Dunn’s storyline and characters are well crafted. This series is great at portraying the valuable work performed by K-9 units — highlighting their loyalty and unconditional love.