This is an alternative solution to the "Who Shot Mr. Burns" mystery. The fanscript is going to take place partly in the timeline that Part 2 took up, as well as what happened afterward. Every single component of my solution is backed up by a kind of evidence either shown or overlooked in the original solution of "Who Shot Mr. Burns". If I say that something exists, there's some sort of evidence of it in the original episodes.
I do take some liberties in filling in some of the gaps that the episodes do not cover, but they hopefully will not contradict what is actually shown in the episodes themselves. The point is that, in theory, everything in this script could have happened (if I don't mess up the continuity in some unforeseen way). Think of it as doing a "Trilogy of Error" to the episode.
This script begins the evening after Waylon Smithers is revealed to be innocent in Part 2. Hey, they didn't show that stuff, so I can do whatever I want with it.
INT, The Simpsons home, master bedroom
HOMER and MARGE are lying in bed, preparing for sleep. Marge stares at the ceiling with a worried expression, as Homer simply stares at Marge invitingly. Marge is too preoccupied with the ceiling to notice.
Marge groans dismissively, which unfortunately means "No" in wife-talk.
HOMER (smoothly, in a bad Southern accent)
How about I just whisper sweet nothings in your ear?
Another dismissive groan. Marge rolls over, facing away from Homer.
Wanna play backgammon?
MARGE (turning around to face Homer)
Does it bother you at all that Smithers was cleared of the shooting today?
A little. It means I lose the Fantasy Burns-Shooter pool at work. I had Smithers.
It also means that the shooter is still at large. It could be anyone... Even someone in this very household.
Damn, I should've bet on them.
Doesn't that thought bother you? Even a little?
Well, it would mean being nicer to the kids so they don't shoot us. And we'd have to raise their allowances.
MARGE (sighing, giving up)
Nevermind. Go to sleep, Homie...
Oh, I get it now. You want to play a game of Clue. I'll be Colonel Mustard!
Marge instead closes her eyes so she can sleep. We are then whisked away to Marge's dream world.
EXT, Town Hall
Marge's dream world is also a flashback to the time of the shooting. The scene is entirely in gray-scale. With the sunblocker in place, Mr. Burns is leaving the town hall meeting, cackling with joy. Marge walks to the parking lot with Maggie. She approaches the car, reaching through the already-open window to unlock the door, and puts Maggie in her car seat. Suddenly, BART approaches.
Hi, Bart. Are you ready to go home?
Mmmmm... Maybe in a minute or two.
Bart brandishes Grampa's Smith & Wesson from his pocket.
Oh, I just have to shoot Mr. Burns. It'll only be a second.
Mr. Burns. He's coming. I have to shoot him soon.
You're not shooting Mr. Burns.
You never let me do anything. You'd totally let Lisa or Maggie shoot Mr. Burns. You never let me shoot anyone.
Well, maybe if you'd clean your room...
How 'bout I shoot Mr. Burns now and then I'll clean my room when we get home.
You're not shooting Mr. Burns. Now give me the gun.
But I need this gun to shoot Mr. Burns. Then what would I shoot him with?
Why do you have to shoot him?
Mom, please stop distracting me. You see, I need to shoot Mr. Burns.
Marge quickly bends down and grabs Bart's shoulders.
Stop saying that! You're not going to shoot Mr. Burns!
...But I've already shot him.
Bart points across the parking lot, where Mr. Burns is already stumbling around with a gunshot wound. The gun in Bart's hands is smoking. Bart leans in close to Marge to whisper something in her ear.
And now you're an accessory.
A gunshot rings out.
A sick expression appears on Marge's face, and she stumbles away from her son to get some help. There is no visible gunshot anywhere on Marge, but she is limping along as if she were. She desperately inches her way around the corner of town hall, heading toward the entrance. She continues toward the main square of town hall, looking for anyone who can help. As Marge stumbles along, she bumps into Mr. Burns, who is also stumbling (due to his gunshot wound). She casually pushes him to the ground and continues on her course.
Marge collapses onto the sundial face-down.