Conversation so far:
What Lord Voldemort in this film?
Voldemort does not appear in Harry Potter and the Half-Blood Prince, although his presence and actions are felt.
How was his presence felt?
he once again declares war, and begins to rise to power once more.

Question: What happens as he gains power?
Self-contained rewrite: What happens as Lord Voldemort gains power in the film Harry Potter and the Half-blood Prince??