A troupe of aspiring college actors board a train bound for California hoping to make it big but must fight to stay alive as they are stalked by a mysterious passenger, who is eager to steal their spotlight and will stop at nothing to get it.

I don't understand how the antagonist is going to steal their spotlight? As Nicholas pointed out, they currently have no spotlight. If his goal is to get fame then surely killing any old random group of people will get the attention he desires. Why these people? What makes them special? If they were famous actors, as Nicholas suggested, then I can understand why this would get more attention but I still see nothing that relates to the hero's goal. Ideally, one hero taking charge, or whoever's alive at the end (as in your other idea on the ship). As variable pointed out why not just contact the train authorities? Or get off the train? A contained setting is great but you need to explain why they can't just get out of the situation that's causing the problem.

This logline gives me more of an idea who the antagonist is but the heroes are blanks? You could always make the antagonist the protagonist? Could be a cool twist - we actually start wishing the actors dead and can't wait to see how he kills the next one. Just gotta make him likeable. Or make the actors incredibly annoying...

What's the incident that kicks the story off? Do they find a body? Does the train stop unexpectedly on a bridge with no means of escape?

Hope this helps.

I don't understand the reason behind the conflict. Why would the killer be trying to steal the spotlight from ASPIRING actors?

The premise works better if they're already famous actors, right? Like, if it's the cast of some huge ensemble film on their way to location, and the killer is taking them out for maximum fame?

Love the premise of a contained setting. Agree with Overlord's comments. I humbly suggest you try getting more of what makes your story unique into the logline.? Just as an example: "after a college actress boards a Hollywood-bound train for a big-picture open call, a mysterious stranger with a hidden agenda and an eerie ability to evade train authorities terrorizes? and stalks her to the point she questions her sanity."? Over the top, but hopefully you get where I'm going with this.? Best of luck.