Those!

Those! is a side quest in Fallout 3 as well as an achievement/trophy.

Summary
A child comes running frantically toward you. His name is Bryan Wilks and giant fire breathing ants have overrun his settlement. As the only survivor and a kid he needs a home and those ants need stomping....

Quick walkthrough

 * 1) Talk to Bryan Wilks and tell him you'll get rid of the ant problem.
 * 2) Enter Marigold Metro Station and talk to Doctor Lesko about his mutant ants.
 * 3) Make your way through the queen ant's hatchery and kill the fire ant nest guardians.
 * 4) Tell Lesko that the way safe with the guardians killed.
 * 5) Find Bryan Wilks and new place to live.

Find Bryan Wilks's father
Bryan Wilks will approach you in the area outside Grayditch, where he tells you that he, his father, and the other dwellers were attacked by fire ants. He then asks the player to look for his father in the town. The father's body can be later found in his house by the shack, killed by the fire ants. You can loot the shack's key from Bryan's father's body. In the shack, you can find a Doctor Lesko's equipment and terminal. Read the notes on the terminal to receive the Marigold Station location and the option to proceed there to locate the source of the fire ants. Also, with a mildly challenging Speech check or the Child at Heart perk, you can convince Bryan to give you the key to a dumpster behind the diner with some valuable loot if you are at a lower level.

Find the source of fire ants
While searching the Marigold Metro Station for the cause of the fire ant infestation, you instead find Dr. Lesko working in a makeshift laboratory. He explains the origin of the fire ants, particularly their ability to spit fire. You can choose to help him reverse the effect or deal with the giant ant queen yourself.

When speaking with Doctor Lesko, if you ask for a "serious incentive," he will offer his old lab coat along with bonus perks. You will find the fire ant queen in the Queen ant's hatchery, beyond Dr. Lesko's lab. It is guarded by numerous fire ant nest guardians. Kill only the fire ant nest guardians guarding the fire ant queen and return to Dr. Lesko for a choice of either the Ant Might or the Ant Sight perk. Alternatively, with a Speech check or a high enough Science skill, you can kill the fire ant queen and convince Lesko that it's the best for humanity, and get one of the perks. You are awarded positive karma if you take this path.

As purely optional objectives, one can hack the terminal in the hatchery to send an inhibitor pulse which will kill all fire ants found in the Grayditch area (excluding those in Marigold Station). In addition, hacking the terminal in the hatchery gives the option to destroy the mutagen sample (which is the FEV). You are awarded positive karma. Having done this, you must pass a speech check or have Science 70 to convince Lesko that it was best for humanity.

Note that it is possible to get both of the rewards (lab coat and perk) and good karma (from killing the fire ant queen or destroying the mutagen sample) without passing the speech check. First, talk with Doctor Lesko for the "serious incentive." Then, go inside the queen ant's hatchery, kill the five fire ant guardians, but do not kill the queen. Go back to Lesko's lab and claim the rewards. Then go back to the hatchery, kill the queen, or hack the terminal to destroy the mutagen sample. You will gain good karma in either way while keeping all rewards from Lesko.

Find a place for Bryan Wilks to stay
The fire ant problem has been taken care of, but the issue of Brian Wilks and his state of residence is still unresolved. First, talk to Bryan and tell him about his father's fate and the fire ants. He is located in the Pulowski Preservation shelter to the right of the diner in Grayditch. You are then given the option of helping him find a place to live. Bryan will tell you that a cousin of his lives in Rivet City. He is talking about Vera Weatherly, owner of the Weatherly Hotel. You only need to find her and mention that Bryan needs a place to live and she'll happily agree to take him in. You will be awarded considerable positive karma for choosing this option. With the arrangement made, simply return to Grayditch and tell Bryan that he can move in with his aunt; he will agree to move out there, and the quest will end. When you return to Rivet City, Bryan will be there.

It's also possible to convince the mayor of Little Lamplight to let him stay there, either with a speech check or via the Child at Heart perk. Be forewarned that discussing this option with the Mayor will prevent the dialogue option for Bryan's relocation from appearing with Vera Weatherly, closing off that path even if Bryan has not been told of his potential new home. Since this is not as good an arrangement for Bryan, no karma will be awarded either way.

Alternatively, you can go to Paradise Falls. Talk to Eulogy Jones, and tell him you have a child for sale. He will offer 100 caps initially, but you can receive 300 caps if you pass a speech check. You will receive a considerable amount of negative karma for this despicable act, and Eulogy will give you the agreed-upon number of caps and a collar to put on the hapless youngster. You will then trick Bryan into putting on the collar, and explain that it will guide him home. Again, the quest will be completed, but no experience points will be given. Bryan will not be seen again, even though Three Dog will mention that he is at Paradise Falls.

You can also tell Bryan that you're unwilling to find him a place to live (or never offer to in the first place), which will end the quest immediately. Bryan will move back into his old house and live in Grayditch by himself. No karma will be gained or lost. However, this option is irreversible, even if you have a change of heart later. For example, even if you encounter Vera Weatherly later in the game, the dialog option for getting her to take Bryan in will not even appear.

Behind the scenes

 * This quest was inspired by the 1954 Sci-Fi horror film Them!, a story about early New Mexico atomic tests that cause common ants to mutate into giant, man-killing ones.
 * Bryan will occasionally make comments from inside the fallout shelter. One of these comments: "Now I know what a TV dinner feels like," is a reference to "Die Hard," in which Bruce Willis says the same line while crawling through a ventilation shaft.

Bugs

 * After completing the quest by sending Bryan to Vera, the screen text may say completed quest "Thos!" instead of 'Those!'.