Ever since the Regulators have been bothering his raider brethren, Junders has sought solace surrounded by the ancient dead, cultivating a shrine to a mystical figure from ancient history named "Lincoln." Plunkett spends his time drinking wine, and polishing his spiked knuckles.
Junders only appears in the game if the player has the Lawbringer perk, and he will attack on sight. If killed, Junders Plunkett will have a unique finger on him which can be turned in for the bounty to Sonora Cruz, with 1000 caps paid as reward. The player does not need to kill Plunkett personally to get credit. Plunkett can die of any means, and the finger will be on his corpse.
Upon looting his corpse, one will find both a generic finger as well as his unique finger.
When the player collects the finger, it stays in their inventory as it is unable to be dropped.
Junders Plunkett's victims may have included Derek Pacion's parents (Louis Pacion and Daisy Roe). The bounty notice states that he is responsible for theft and murders in Canterbury Commons; this matches up with the fact that Derek Pacion's parents lived in Canterbury Commons and were murdered by Raiders. If this is true, it also makes sense why the bounty on him would be so high because Uncle Roe would have taken the murder of his sister and brother in law very personally, and being the Caravan manager means he has a lot of financial clout, so this could explain why the bounty on Junders Plunkett is so much higher compared to other criminals.
The following is based on unverified behind the scenes information and has not been confirmed by canon sources.
Junders Plunkett's name may be a reference to the Irish Revolutionary figure Joseph Plunkett, who was the youngest signatory of the Irish Proclamation of the Republic at the beginning of the Irish Revolution in 1916. This is supported in that Bobblehead - Luck, in which Vault Boy is dressed as a leprechaun and is holding a four leaf clover, is found in his basement.
End of information based on unverified behind the scenes information.