In 353 AD, Constantius II died (but only the one that ruled the West!) and Julianus (the Apostate) rose to the Western Throne! So now the eastern Constantius II continues to rule while the WRE is in a lot of trouble with it's full bag of hostile barbarians, frequent rebellions and now, a pagan August!
+ it turns out that the Franks actually poisoned Constantius II on the battlefield!