"Old Man" Marley was Kevin McCallister's kindly neighbor who was rumored to be a serial killer called the South Bend Shovel Slayer.
At some point, Marley had a heated dispute with his son, which ended with the two refusing to speak with each other anymore. The estrangement caused Marley to lose contact with the rest of his family, including his young granddaughter, whom he adored.
For a long time, there were rumors that Marley was the "the South Bend Shovel Slayer," who had murdered his entire family and half of the people on the block with a snow shovel in 1958, but avoided arrest, due to lack of evidence. In addition, he kept his victims in his bucket of salt, using the salt to turn dead bodies into mummies.
Crossing Paths With Kevin
Before the McCallisters left, Buzz, told Cousin Rod, and Kevin the full rumors about Marley, as the three watched Marley shovel and salt the sidewalks from their window, Rod suggests that Marley's shoveling and salting is just him trying to be nice, but Buzz disagrees. A moment later, Marley looked up in their direction, but the three quickly hid behind the curtain.
After Kevin was accidentally being left home alone, the Wet Bandits started to break into the house. Kevin quickly turned the lights on, causing them to flee, while Kevin hid under the bed. A moment later, Kevin, rushed outside, calling to them, that he was "not afraid anymore." However, upon seeing Marley approach him, he turned and ran back inside his house, afraid and screaming.
Later, Marley went to a drugstore, where Kevin also happened to be, to buy a toothbrush. The boy looked up, saw Marley glaring at him, and stepped away a little before running off, accidentally shoplifting the toothbrush. A clerk and officer started to pursue Kevin, but he got away.
On Christmas Eve, Marley went to a local church to watch his granddaughter who was about the same age as Kevin, rehearse with her choir for Christmas mass. He ran into Kevin, who was still surprised to see him, and pleasantly greeted him. He then dismissed the rumors about him, while also explaining to Kevin the difficult situation with his family. Kevin suggested Marley to call his son, and Marley admitted that he was afraid to, thinking his son would refuse to speak with him. Kevin told Marley that he should call his son, and whether or not his son talked to him, he would know and he would not be afraid any longer. Kevin mentioned that he'd always talk to his own father, no matter how mad he was, and Marley should also do it for his granddaughter, who probably missed him and the presents.
Later, after Harry and Marv captured Kevin at the Murphys' house, and Harry was about to bite Kevin's finger, Marley intervened and hit both burglars with his snow shovel (knocking them unconscious) before taking Kevin back home.
By the next morning, Marley had made peace with his son. As he hugged his granddaughter and daughter-in-law, Marley saw Kevin through the window of his home. The two waved and Marley went into his home with his family.
- You can say hello when you see me. You don't have to be afraid. There's a lot of things going around about me, but none of it's true. Okay?
- (About the church) This is the place to be if you're feeling bad about yourself.
- How you feel about your family is a complicated thing.
- Deep down, you'll always love them. But you can forget that you love them, and you can hurt them and they can hurt you, and that's not just because you're young.
- You're always welcome at church.
- You can be a little old for a lot of things, but you're never too old to be afraid.
- (After hearing about Kevin's experience in the basement) Basements are like that.
- (Smiles) Merry Christmas.
- (While taking Kevin off the hook) Come on. Let's get you home.
- In the novelization for Home Alone, Marley says to Kevin, “You don't have to be so scared of me. All that stuff you hear about me — none of it's true. Just the product of someone's overactive imagination."
- The Pigeon Lady in the second movie has a similar role to that of Marley. Both appeared menacing at first, but turned out to be quite friendly, and came to Kevin's rescue when Harry and Marv had him trapped, while wearing the same boots. Mr. Prescott from the fourth movie also has a similar role, but instead of Harry, Marv's wife Vera appears.
- It is not known how he entered the Murphy household to rescue Kevin after his capture. But it is implied that he left for his house after Kevin leaves the church and he saw the bandits breaking in to the McCallister household. It is also presumed that he decided to rescue Kevin when he later saw the bandits following the latter fleeing to hide in the Murphy house, even witnessing the duo breaking in the said home.
- He is likely named after Jacob Marley from A Christmas Carol, who warns Ebenezer Scrooge what his life would be like if he continues to act insensitive towards others, just as Old Man Marley warns Kevin how lonely his life would be without his family.