Tailing the Tomboy

 refers to an unmarked quest in the Fallout 3 add-on Point Lookout.

Walkthrough
When arriving at the Riverboat Landing for the first time, the Lone Wanderer is approached by a woman named Catherine. She is looking for someone to find her daughter Nadine who has recently left with Tobar for Point Lookout and convince her to come back.

Nadine can be found inside The Ark & Dove Cathedral, now a member of the local tribe but not all that thrilled by it. She tells you about someone cutting portions of the contestants' brains out during the ritual and wants to meet up with you at Point Lookout Pier once she has confirmed her suspicions regarding who that might be.

Once you meet her there, she reveals Tobar is the one who is collecting brain portions and that she will take the Duchess Gambit as compensation for what he has done. Now she'll agree to meet her mother back in the Capital Wasteland who in turn rewards you with some Refined Pungas.

Reward

 * 10 Refined Pungas
 * 300 Bottle Caps