Mesmetron

The Mesmetron is a prototype non-lethal weapon in Fallout 3.

Background
Developed by Implied Hypnotics, Inc. before the War, the Mesmetron is an experimental "non-lethal subjugation device" provided to the United States military for them to assist in experimental trials. It operates by sending a series of waves that the brain attempts to decode, but because the synapses are being overwhelmed by the neural static, the brain becomes confused and switches off important higher-level mental functions and voluntary motor control, leaving the target extremely susceptible to suggestion. Still in its testing phase, the weapon was found to have the potential to trigger two undesirable side-effects: extremely increased aggression or a "resonant brain wave feedback loop" which resulted in spontaneous cranial eruption. Despite the prototypical nature of the device, several were attached to robobrains to add in interrogation processes. (Officially noting the 10-15% casualties due to spontaneous cranial eruption.)

The model given to the Lone Wanderer in Paradise Falls was scavenged from an old military base by Grouse Jurley. The Mesmetron is invaluable to slavers, making it a cakewalk to capture slaves, which are left senseless by the Mesmetron waves. However, caution must be exercised when using the Mesmetron around already collared slaves, because the waves interfere with the collar's radio signals and cause it to unintentionally detonate.

Characteristics
When used on the specified quest non-player characters, it puts them into a hypnotic stupor, allowing the player to rob and enslave them (by putting a slave collar on them) and send them to Paradise Falls. It also appears to work on many other non-player characters (aside from quest related ones), but can simply send them into a berserk frenzy in which they become hostile towards the player and every other non-player character in the area. Occasionally, victims will run several steps before their heads explode.

It uses Mesmetron power cells as ammunition. Grouse provides the player with 50 Mesmetron power cells free of charge, but will also sell you additional power cells at the fairly steep price of 200 caps for 10 power cells. This gives you the opportunity to make an additional 2500 caps every time you purchase more power cells (provided you successfully capture all 10 slaves). An additional 71 Mesmetron power cells can also be found in the St. Aubin Medical Facility in the Point Lookout add-on.

The Mesmetron can fire a total of 2475 waves, or 495 full cells, before breaking.

Using the Mesmetron
As previously mentioned, using the Mesmetron on an non-player character can have three different outcomes. These effects vary and are generally unreliable, so it is advised to save before using this weapon on anyone important. Due to the fact that using the Mesmetron is considered assault, it is advised to "mezz" someone while not detected. Be aware that mezzing anyone who is already wearing a slave collar will cause the collar to malfunction and explode, killing the victim. Hostile non-player characters who were mezzed can also be turned friendly by being freed by the player (high Science skill required). An analysis of the Mesmetron's effects is as follows.

Mesmerize/Stun (50% probability)
This effect stuns the target for a few seconds, during which time the victim will stand with their head swaying from side to side and it is possible to engage them in conversation. Some characters cannot be stunned, resulting in the probability of the Frenzy effect to be raised to 80%.

While in conversation, there are three options. The first convinces the character to allow themselves to be robbed of their possessions and will open up the victim's inventory, allowing any item to be added or removed. The second slips a slave collar on the character (instantly resulting in negative Karma). The third simply tells the victim to "walk it off"; this exits the conversation and make the character resume what they were doing.

The second set of dialogue options is unlocked by slipping a collar onto the victim. The first is the "cruel" way to tell the victim that he is now a slave ("...your head will explode!"), the second option allows access to the slave's inventory, and the third option is a slightly friendlier way to inform the victim of his/her "new occupation" ("...nothing personal").

If the character is not spoken to before the stun effect wears off, he or she will become hostile to the player.

Frenzy (30% probability)
This alternative effect causes the victim to go into a state of frenzy, attacking anyone nearby (most likely the player), and causing all other characters to turn on them.

Spontaneous cranial eruption (20% probability)
This alternative effect of the Mesmetron may not be the most useful, but is definitely the most spectacular. When victims are affected by the Mesmetron in this way, they will become hostile (and either run, stand still, or attack) for just a moment before their heads literally explode. This effect will instantly grant negative Karma (if the victim was good/neutral) and make any nearby non-player characters who were not hostile to the victim become hostile to the player.

Variants

 * Microwave emitter, a similar weapon designed for killing targets as opposed to stunning them, found in the St. Aubin Medical Facility at Point Lookout.

Location
The Mesmetron is given to you by Grouse, the Paradise Falls entrance guard, when you start the quest Strictly Business.

If you don't want to take the quest, you can obtain the Mesmetron by killing Grouse and looting his corpse. You have to kill him to obtain the Mesmetron, as it cannot be pick-pocketed. If you do this, you cannot get a slave collar and thus can't enslave non-player characters. You can still use the Mesmetron to frenzy or stun and rob non-player characters.

Related quests

 * Strictly Business
 * Strictly Profitible

Bugs

 * Freshly enslaved non-player characters will often be reported by Grouse to have died once the Lone Wanderer arrives at Paradise Falls. This is caused by a condition in the Mesmetron effect script which automatically moves the slave to Paradise Falls—indirectly marking them as dead in the process—once the non-player character is no longer being actively rendered. Aside from leaving the non-player character's immediate vicinity, numerous actions have a random chance to cause an non-player character to stop being rendered, including accessing the Pip-Boy, facing away from the non-player character for a certain period, or even accessing the game menu.
 * A third-party bugfix has been released which addresses this issue: Mesmetron and Enslavement Fixes at Fallout 3 Nexus
 * Attempting to remove a collar from a non-player character enslaved by the Lone Wanderer (other than Susan Lancaster, Flak, Arkansas, and Red) can result in a crash to desktop, depending on the non-player character's actions immediately prior to the conversation. Crashes seem more likely to occur as the time between enslavement and collar removal increases, but are less likely if the enslaved non-player character is not on their usual route.
 * Removing a collar from a non-player character who was mezzed while in combat may cause them to die once the collar is removed. This seems to happen more often (but not only) when the non-player character was stripped of their armor and/or at low health before being mezzed. The non-player character's death does not appear to be attributed to the player and will not give XP.
 * "Mezzing" characters who are seated, leaning on a wall or lying down may cause them to spin rapidly in place before their heads explode.
 * When you untie a captive and then use Mesmetron while he or she is getting up, the person will be stunned and not be talkable. When the stun effect passes, the person will still appear to be tied but can no longer be engaged in conversation.