* Dracula's growing weakness: As the vampire's hold on Harker weakens due to his exposure to the daylight and the vampire's increasing need for blood, Harker becomes more capable of independent thought and action.
* Mina's influence: Harker is bolstered by his connection to Mina, who actively seeks information and ways to help him.
* The arrival of Van Helsing: The arrival of Van Helsing and the other vampire hunters turns the tide. They bring in the tools and knowledge needed to combat Dracula, creating a distraction that allows Harker to escape.
Harker's escape is not a dramatic chase or cunning strategy. Instead, it's a gradual shift in power dynamics brought about by the combined efforts of the vampire hunters and Harker's own will to survive. He doesn't escape the castle on his own, but he becomes a participant in his own liberation.
This subtle escape emphasizes the themes of reliance on others, the power of the mind and will, and the importance of working together to overcome evil.