After his wife is murdered a brilliant scientist travels back in time to save her- but at what cost?

One more thing: There are two reasons to ask a question…

1: To get an answer, but the reader doesn’t know the answer.
2: Because it is rhetorical, But rhetorical assumes the answer is obvious but since the reader doesn’t know what the cost is, it isn’t rhetorical either.

As a result, asking a question that is neither rhetorical or nor something the reader can answer adds no information to the logline and is just confusing.

I would try to write a version of this logline without the tagged on question?at the end, and add the stakes into the logline so the reader knows what the possible cost could be if the lead character messes with the timeline.