Some versions of the song give the lyrics as:

...sees her ticket's "through."

In other words, he sees that she has a "through" ticket, which means (I think) that she is supposed to continue her trip by transferring to another train, probably at the terminal—as opposed to a "local" ticket which would mean that she will get off at some station along the current route. He is interested in knowing this because it enables him to plan when he will make his move.