ER S05E08 The Good Fight (aka A Perfect Match)
After a car accident, a girl and her father are brought into the ER. The girl, badly injured and needing surgery, shares a rare blood type with her father; when Lucy returns to the father’s exam area so she can draw his blood, she finds that he has bolted. After exhausting all other possibilities, Benton operates on the girl without blood. Meanwhile, Carter and Lucy have been traveling throughout the city trying to find the father; they encounter a number of obstacles, not the least of which is a fall in which Carter dislocates his shoulder. With some astute detective work, they find the father — who has been waiting for news about his daughter in the diner across from the hospital.