Doctor Blood Cross is a simple doctor. Trying to cure new dieases that pop up here and there. One day, a patient came into his office and asked for his help because her brother has become infected with some new disease. Of course he accepted, and cunducted a few experiments to cure this new disease. Instead of curing it though, He just made it worse. Shocked by this, he gathers a few others with the same disease, and tries his best to find a cure for it. Only causing the disease to be more unstable. Soon, more of Equestria gets infected with this disease, and now Blood Cross has to find a way to stop it before it becomes a pandemic and destroy all of Equestria. Thing is … he can't do it alone. That's not the worst of it … turns out that an old villain has returned as well, and his past comes back to haunt him.