Harry ends up with a cauldron full of Felix Felicis potion inside his system (which should have been a lethal dose). His saving grace? The basilisk venom having acclimated his body to poisons, so instead of a whodunit, we have a drugged up Harry who feels utterly invincible.
Unlike other cases of the potion inducing a lethal accident, his resistance sets him up for the greatest of time of his life. Only issue? He has no clue why he needs to go buy a shovel and a tarp.
I really liked the idea of someone trying to poison Harry and instead let Harry fix his life.