As the clip starts, Mer is walking along a hallway of Grey Sloan Memorial when a woman beckons her for help, saying that she happened across a little girl in dire need of help. Mer follows the woman out into the ambulance bay and sees the girl seated on a bench, clearly in extreme pain.
Mer runs over to her, and we see what she sees — but it's hard to tell what we're looking at! The girl's abdomen is seriously distended, almost as if she has a huge baby bump… but she seems too young to be an expectant mother, right?
Unfortunately for us, ABC's synopsis for the episode sheds no light on the medical mystery. Here's what the network had to say: