Complex sentence: He is told he has been found delirious in a river near Budapest and, naturally, no one believes him about what happened at Castle Dracula until Van Helsing finds the two punctures on Harker's neck.
Split into simpler sentences: He is told he was found delirious in a river near Budapest. Naturally, no one believes his story about Castle Dracula until Van Helsing finds the two punctures on Harker's neck.