Mycroft was depressed, Lestrade felt betrayed, and cake? Well, cake was planning its revenge on the detective inspector. Cake was very crafty, you see, so it didn't take too long to think of a cunning plot that would ruin Greg Lestrade for good. It would look like a suicide, because no one would ever suspect cake.
It was before work, and Lestrade was brewing himself some tea to help wake himself up. He didn't want to look at Mycroft. He couldn't.
He went to the fridge to grab the milk, and bright orange icing caught his eye. It was most likely Mycroft's, but he didn't need that fat oaf. He had ate enough already. So he grabbed the cupcake and ate it, wishing he hadn't in the end, because he now felt sick.
Mycroft unfortunately had work today too, so he wasn't long getting out of the bathtub (yes, the bathtub. Even the British Government gets shouted at for being a cheating bag of dicks and thrown out of his own bed) as he made his way downstairs into the kitchen. He stopped dead at the ungodly sight: on the floor lay Gregory Julio Ricardo Montoya de la Rosa RamÃrez Lestrade, nothing now but a lifeless body.
"You monster!" Mycroft shouted at cake, who was watching the sight from the kitchen table with a sly, triumphant smirk. The crumbs on his lover's face said it all.
Mycroft started rummaging through one of the kitchen drawers until he found what he needed. Yes, perfect. He wouldn't have to deal with this problem much longer if cake was gone. He couldn't stand it.
"What the hell do you think you're-" cake was cut off as Mycroft began stabbing into the glorious, sweet smelling sponge. Cake screamed out on pain, and jam splattered everywhere; all over the floor, Mycroft's face and suit, the knife.
Soon cake's screams went quiet, and it lay still, not struggling any more or trying to get Mycroft away.
"You're nothing to me." he snarled, taking out a match and lighting cake on fire. He watched the flames burn that once, beautiful icing, until it was nothing but a melted mess, soulless like Mycroft himself.
He grinned insanely and let out a high pitched evil laugh that echoed for all of London to hear. Everyone would know that was his warning. They would know something dangerous was upon them. Yet they wouldn't be able to do anything about it, because not even Robert Downey Jr. in his Iron Man costume could save them. No one was safe.
And that is the story of how Mycroft Holmes became the crazed cake killer of London.