a movie where everyone dies at the end?

Hi.

I'd like to combine these two sentences.

1. I watched a movie.
2. In the movie, a man kills all his enemies.

Now, let me put them together.

3. I watched a movie that a man kills all his enemies.

Well, this sounds awkward, doesn't it?
Would it be natural if I replaced 'that' with 'where'?

4. I watched a movie where a man kills all his enemies.

I hope to hear #4 sounds okay.

Would you please leave comments?
I'd really appreciate it.