Mel is an old associate of Bobbi No-Nose, who previously worked with her on a few jobs before he got in trouble with the law. He was caught trying to reprogram the automated bartender Wellingham, from the Colonial Taphouse, to give him free beer. This led to Mel being arrested by security and his incarceration in Diamond City's lockup. According to the jailer, he would have done the same had he the know-how.
Before he was arrested, Mel was working on an advanced utility eyebot named Sonya and an improved version with better offensive capabilities, Sonya Mk.II.
When the tunnel workers she hired to assist with her heist called the Big Dig are driven off by mirelurks, Bobbi sends her new gun, the Sole Survivor, to free her old associate from jail, who has the robot capable of speeding up the digging.
Mel can be found as a random encounter later on. He can be spoken to but no matter what is said he is not happy and just keeps walking. Sonya Mk. II follows him.
Mel will be flirtatious toward a male Sole Survivor when the sarcastic dialogue options are chosen in conversation with him, and comments on his looks when talking with Bobbi. He does not flirt with a female Sole Survivor.
Mel may join the player character simply by stealing the cell key.
When activating a Port-A-Diner, Mel will say "Yeah, I wouldn't touch that pie. I don't trust anything that looks that perfectly preserved after 200 years."
PCXbox One Mel may become hostile to player character while inside the tunnel during the quest, The Big Dig for unknown reasons. [verified]
In the console, use prid 0011fc2d to target him. Type recycleactor to reset him. Then use 0011fc2d.moveto player to return him to player's location.
Playstation 4 Mel may stay seated after getting hurt. You can still proceed as usual through the quest line and if this happens while he is in the Dig he should randomly appear behind you after you call for Sonya. [verified]
PCPlaystation 4Xbox One After completing The Big Dig, Mel may remain in the final excavation room and will become completely unresponsive. [verified]