Dr. Valerie Monroe is a character portrayed by Sara Holden in the ABC crime series Castle. Doctor Valerie Monroe was a physician at County General Hospital in New York. Some months earlier, she treated former drug lord Cesar Calderon after he suffered a heart attack, Calderon subsequently asking her to become his personal physician. Monroe spent five nights a week at Calderon's penthouse to see to his care, with their relationship becoming close over the following months- to the point that Calderon gave her a unique bracelet that had belonged to his mother-, although Calderon denies that there was ever any physical romance in their relationship.