Fallout: New Vegas/The Finger of Suspicion

In Caesar's Fort, you can speak with Vulpes to get a quest to find Martina Groesbeck. She is located within the Vault 21 Hotel.

You may find in her room located at the southern edge.

As soon as you try your approach, the Omerta thugs will stop you, telling you to turn around and leave. With a Speech of 50 (or, you can convince them to leave Martina alone; otherwise you need to defeat the thugs in combat. However, convincing them to leave peacefully is the best option, since it means that it is a more permanent solution.

However, when you speak with Martina, she will mention that she was actually reporting to the NCR. If you advise Vulpes about this, he will mention that this is correct. This will commence the mission I Put a Spell on You at Camp McCarran.