Lacey Miles becomes the unexpected sole guardian of her young niece. Knee-deep into an investigation of a sleeper cell, Lacey finds that motherhood is a lot more perilous than she expected, so she hires a nanny with an impeccable resumewho's a far cry from Mary Poppins. Beneath his friendly demeanor, Jim Mercer is a former Marine turned undercover agent, tasked with ferreting out the terrorists targeting Lacey and her loved ones. Jim may be the ultimate caretaker, but the closer Lacey comes to blowing her case open, the more Jim's true identity is revealed. And the deeper he falls for this vulnerable little family.