"Anderson, these theories of yours won't bring him back," Lestrade says exasperatedly. Unfortunately for Lestrade, these words have no affect on Anderson, as he had spent a good amount of time on this particular theory and is completely convinced that it was the only way Sherlock Holmes could have faked his own death.
"Listen, I put up with these stupid speculations at first but now they're just getting ridiculous!"
"No! This is really the way he did it! I've gone through every detail and I'm sure there is no other way it could have been done!" Anderson argues, desperate for Lestrade to hear him out. Every flaw with his previous theories had been amended; Anderson genuinely believes that he had uncovered the secret behind Sherlock's fall.
"Go on then. You've got ten minutes," Lestrade relented, knowing completely well that Anderson will simply harass the poor detective until he'd agree to listen.
Anderson rakes his hand through his dark hair, preparing himself to convince Lestrade that Sherlock's intellect has helped him to both rid himself of his criminal charges and keep his life.
"First off, Sherlock had to have known all the different scenarios that could've happened on that roof. He was prepared for everything and obviously had people on the ground. He also knew, however, that John was about to arrive in that taxi any minute. In order to distract John, he called him and rattled on about how he was a fake and whatnot. Meanwhile, two men take Moriarty's body from the roof and disguise him as Sherlock-"
"How would that even work exactly? Moriarty looks nothing like Sherlock!" Lestrade interrupts, grasping at an excuse to end this conversation immediately.
"Well, Sherlock would have had a mask of his face already made, and from there all that was needed were some contact lenses and clothing that matched what John had seen Sherlock wearing on the roof," Anderson replies impatiently, as if to imply this is an obvious detail.
"Oh yes! That doesn't sound completely insan-"
"Just try your best to keep up, Detective. Anyway, after that, Sherlock would've jumped from the roof, while simultaneously arranged for a biker on the street- clearly from his homeless network- to knock John to the ground. Now, what John didn't notice in his panic is that Sherlock had a bungee cord strapped to his belt that was tied to something on the roof, perhaps the chimney or something. Meanwhile, Moriarty's body is planted right where Sherlock ought to have landed, and blood from a blood bag is poured all around him so it looks like he's suffered a blow. So, as John is on the ground, Sherlock is brought back up with the tension of the cord... now this is where I had some trouble. Where could Sherlock go when he's suspended in mid air? And how could he make sure John didn't see him? Well, it took some time but I figured it out eventually: Sherlock broke through one of the windows of the hospital, and landed right in front of none other than Molly Hooper. In pure Sherlock fashion, he unhooks the bungee cord, brushes off the broken glass, and kisses her passionately before disappearing down the hallway. Meanwhile, Sherlock had enlisted the help of Derren Brown, who hypnotized John temporarily so Sherlock would be given more time to escape without John knowing. After adjusting the lost time on John's watch, Brown creeps away and John is none the wiser."
"Oh for Christ's sake, Anderson! Are you planning on wrapping this up anytime soon?!"
"Just listen! So now John gets up, unaware that he's lost time, and his doctor instinct tells him to check the pulse of Jim Moriarty's body, which is nonexistent. Of course, since he's probably suffering from a minor concussion, and just fought through a large crowd of more hired actors, he doesn't even recognize the subtle differences in 'Sherlock's' appearance. Since he's checked for himself that his beloved friend is in fact dead, he lets the paramedics take him away. And now Sherlock walks away a free man. Don't you see?! It's bloody brilliant!" Anderson finishes, slightly out of breath and eyes wide open, searching for an ounce of belief in Lestrade's expression.
"Bollocks!" cries Lestrade, "You've really lost it, haven't you?" he begins to walk away from the forensic scientist, shaking his head at the man's pathetic attempts to cope with his guilt.
"Let it go. Sherlock's dead."