A night after Wonderbolt training, Rainbow Dash feels sick. Thinking she can just sleep it off, she unfortunately wakes up in the morning and feels worse and Soarin starts to notice it. Instead of staying in bed, she decides to keep training even though she feels terrible. When Fluttershy comes over to see her, she notices Rainbow Dash's behaviour and soon picks up that she's not feeling well even though Rainbow Dash didn't mention anything. Soon, Rainbow Dash's condition gets worse and worse until she is finally forced to stop.