After installing the DLC and spending a few minutes ingame, a message will appear on your screen informing you of a riverboat, the Duchess Gambit, that has docked at Riverboat Landing, which is located to the east of Arlington Library in southern downtown DC. When you arrive at the dock, you can speak to a woman named Catherine about her missing daughter, Nadine (this starts the "Tailing the Tomboy" quest if you accept). To travel to Point Lookout you must speak with Tobar and buy a Riverboat Ticket. After you have acquired a ticket, enter the room near the back of the boat and activate the cot to begin your journey.
Once you arrive at Point Lookout, follow your quest marker to Calvert Mansion and go inside. When you enter, you should notice a ghoul in a white business suit and two dogs fighting several tribals. Kill the tribals then speak to Desmond. Follow Desmond to the bathrooms and kill the tribals in the area.
After all the tribals are dead, follow Desmond to another part of the Mansion. Go through the doors he opens, and kill the tribal that falls from the ceiling. Proceed through the area, killing all tribals you encounter. Once you get to the source of the invasion look for a partly broken inoperable door with a red pressure vessel in the room on the other side of it. Shoot at the pressure vessel or toss a grenade inside to trigger an explosion that seals off the area. Follow Desmond to the next area.
In the next area, you will only go several steps before falling two stories to the basement floor. The floors break your fall slightly on the way down, and you suffer no damage. Continue moving your way through the mansion, killing tribals. As with the other side, look for a red pressure vessel on the opposite side of an inoperable door, and blow it up to seal off the entrance. After closing up the final breach, follow Desmond back to the main room.
Once you return to the main entrance, Desmond will inform you of an impending attack. Follow his advice and lay down any mines you have. You can find some mines in a lock box behind Desmond's upstairs barricade. When placing your mines, keep in mind that the tribals will enter from a multitude of directions, not just the front door. The tribals enter in waves of 3-5 from, in order, the upper right, lower right, lower left, and center doorways. Since they must enter through the narrow doorways, area of effect weapons will be very helpful here. Weapons with large bullet spreads, such as shotguns or miniguns will also be helpful. After fending off the last of the tribals, you must speak to Desmond, who gives you the Superior Defender perk. The conversation leads into the next quest, Walking with Spirits.
Your followers are automatically fired when you travel to Point Lookout (by activating the cot).
While sailing to Point Lookout you can see a tracker walking towards the bay
There is a mini nuke under the buoy that is closest to the dock along with other goods.
Tobar claims "In Point Lookout, you'll find fresh-grown food, mysterious locales, and treasures as-of-yet un-looted. But keep your wits about you, because you'll find more than a few exotic critters and inhospitable locals. So stay here if you're not man enough!"
If you leave any tribals alive while clearing the East and West Wings they will be immediately killed (via a scripted action) once the last breach is sealed.
It is advisable to finish the Tailing the Tomboy quest before you decide to leave as having to buy tickets from Tobar can be a very expensive affair.
If you followed Desmond's suggestion to place mines before or during the final assault in the Calvert Mansion, Desmond may set off any remaining ones and become hostile as a result. It is therefore recommended that you do one or more of the following:
Avoid placing mines anywhere other than near the boarded-up doors.
Run ahead of Desmond at the end of the final assault and retrieve any remaining mines.
ps3 Upon arrival at the pier, the quest may get stuck on the objective "Leave the Duchess Gambit". If this is the case, simply go directly to Calvert Mansion and the next objective will be added, although there will be two quest markers as a result.
pcps3xbox360 When helping Desmond clear the mansion, he may stop in the bathroom and only say "Help me kill these bastards while I think up a plan" despite all the tribals in the area being dead, making it impossible to continue the quest. If this happens in the PS3 version, incapacitate Desmond. After he regains consciousness, he will continue with the quest. [verified]
ps3 When sealing off areas with grenades/bullets be sure to stand back as standing too near the door can result in being jammed inside the door unable to move causing a reload. [verified]