Thought Control

 is a Fallout 3 quest that is added to the game with the Point Lookout add-on.

Talk to Desmond
When you talk to Desmond about Calvert (the brain that you spoke to), he tells you about his past with Professor Calvert and the Calvert family in general. He then tells you to plant a Cogwave Jammer on the Ferris Wheel that will disrupt the messages that Calvert has been trying to send throughout the Point Lookout area. Once you near the Ferris Wheel, you can hear Calvert’s voice trying to persuade you to destroy the device that Desmond gave you. There can be an error here though. When you walk up to the ferris wheel, Calvert may have not contacted you, the Cogwave Jammer can not be placed. This can be fixed by roaming the area, specifically to the item shop, and then you will be able to make the choice.

To plant or not to plant
Once you reach the ferris wheel, you have two options:

Side with Calvert

 * The mansion blows up and there is a small loot inside the panic room.

Side with Desmond

 * Plant the jammer and activate the ferris wheel. After this is done, two things will happen. First Calvert's voice breaks up as the jammer does it's job and second a group of Tribals will attack you. Eliminate the Tribals and return to Desmond.

Return to Desmond
When you approach the Calvert Mansion, it immediately explodes as parts of Desmond's fail-safe. As a result of the explosion, you are knocked to the ground. Once you stand back up, walk to the middle of the house and find Desmond in his panic shelter. He begins to tell you how angry he is that his dogs were killed and that Calvert was so close to the mansion. He then states that the 200 year long feud between him and Calvert is going to end right now.

Reward
300 XP