The Equation of Hearts

Elena lives her whole life running away from a past that haunts her. So when she finally reaches success, she's desperate to keep it that way.
What happens one day when she's met with a boy claiming to be her son? What does she do when the boy she's never met claims his father in danger? Who is his father?
In a sudden turn of events, Elena's met with a new bodyguard who not only digs up a past she wanted to deny, but also plants the doubt of "what could have been". She wants to help but how can she risk the life she gave her whole soul to?