Mesmetron The Mesmetron is a unique weapon in " Fallout 3 " . Background . The Mesmetron is an experimental pre - War " non - lethal pacification " weapon that was being tested in the months immediately preceding the Great War . It operates by sending a signal pulse into a human target ' s brain that scrambles higher - level mental functions , 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 spontaneous cranial eruption . Characteristics . When used on the specified quest non - player characters , it puts them into a hypnotic stupor , allowing the player character 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 turn hostile to the Lone Wanderer 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 , starting out with 50 power cells . Grouse will also sell additional power cells , but at the fairly high price of 200 caps for 10 power cells . This gives the opportunity to make an additional 2500 caps every time one purchases more power cells ( provided all 10 slaves were successfully captured ) . An additional 71 Mesmetron power cells can also be found in the underground lab in the " Point Lookout " add - on . Durability . The Mesmetron can fire a total of 2500 waves , or 500 full cells , from full before breaking . Using the Mesmetron . As previously mentioned , using the Mesmetron on a non - player character can have 3 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 undetected ( Stealth Boy s and the Chinese stealth armor will come in handy here ) . 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 character ( high Science skill required ) . An analysis of the Mesmetron ' s effects : 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 , in which case the probability of the Frenzy effect is raised to 80 % . While in conversation , there are three dialogue options : The first convinces the character to allow having their things taken ( by either telling them it ' s a magic trick , that there is a thief on the loose , that the player character thinks they stole something from them , or by just telling them to give their things ) and will open up the victim ' s inventory ( even what they are wearing / using ) , allowing the player to remove or add any item . The second slips a slave collar on the character ( instantly netting negative Karma ) . The third simply tells the victim to " walk it off " ; this will exit the conversation and make the character resume what they were doing ( assuming no onlookers turned hostile ) . 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 they are 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 their " new occupation " ( " " . . . nothing personal " " ) . If the character is not spoken to before the stun effect wears off , they will turn hostile towards anyone they can see , that includes the player character . Frenzy ( 30 % probability ) . This second effect causes the victim to go into a state of frenzy , attacking anyone nearby ( most likely the player character ) , and causing all other characters to turn on them . The onlookers may also turn hostile to the PC if caught stunning the victim . This method can also be a reliable way to get rid of victims without attacking them or getting negative Karma . This is dangerous , however , especially if one of the enemies has any high - damaging weapons . Spontaneous cranial eruption ( 20 % probability ) . This final 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 turn hostile ( and either run , stand still , or attack ) for just a moment before their heads literally explode . This effect will instantly give negative Karma ( if the victim was good / neutral ) and turn any nearby non - player characters hostile to the player character . Location . The Mesmetron is given to the Lone Wanderer by Grouse , the Paradise Falls entrance guard , upon starting the quest Strictly Business . If deciding not to take the quest , the Mesmetron can be obtained by killing Grouse and looting his corpse . It cannot be stolen from him , meaning he needs to be dead to get it . If this is done , it ' s no longer possible to purchase any Mesmetron power cells nor slave collar s from him , thus one can ' t enslave non - player characters . The Mesmetron can still be exploited to frenzy or stun and rob non - player characters , however .