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.

When 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 agrees to meet her mother back in the Capital Wasteland and you are no longer charged for using the ship.

After the conversation, Tobar can be found in the engine room of the Duchess Gambit. After a short conversation he turns hostile and attempts to kill you. After you kill him, his body has some bottlecaps, the Grifter's Fit. a Roving Trader Hat, .44 Magnum Rounds, a Scoped .44 Magnum and other items. You can also find the portion of your brain he removed nearby.

Once you travel with Nadine to the Capital Wasteland, Catherine rewards you with some Refined Pungas and 300 caps.

Reward

 * 10 Refined Pungas
 * 300 caps
 * Free passage between the Capital Wasteland and Point Lookout.
 * Lump of Brain