The nail polish, spilling from the bottle that you carelessly dropped upon the carpet, goes to work quickly, its acetone component eating away at the carpet and seeping through the floorboards beneath to drip into the light fitting in the ceiling of floor beneath yours, wearing away at the power cable and the plastic around the screws holding the cheap light fitting up. Moments later, you hear a faint crash as the light fitting falls to the floor, the light bulbs smashing. The occupant of the apartment directly beneath yours is not home at the time this happens, but returns home late that same evening, and without the ability to turn on the light, he does not see the broken glass of the light bulb, and having just taken off his shoes as he came through the door, steps on the broken glass of the bulb- you hear a scream.
That scream, remarkably loud due to the unusually low pain threshold of the tenant of the apartment beneath you, wakes up his next door neighbour, a paranoid old man, somewhere in his mid eighties, who has slept with a loaded gun under his pillow for the last thirty years or so, not trusting the fact that he lives on the seventh floor of an apartment block to keep him safe from thieves coming through his window. As the old man wakes suddenly, he brings the gun up, opening fire before he could even take stock of his surroundings, shooting straight through his window at the gang of petty thieves he imagines to be breaking in to steal his paltry collection of valuables.
On the pavement beneath, a handful of police are mustering up for a drug raid on an apartment in the same building- still waiting for the rest of their assigned number to turn up before making their move, when they hear the gunshot, all bets are off and they go in with only the six of them, storming into the teeth of an improvised explosive device waiting for them behind the door of the abandoned apartment, which kills them all, including the most senior of the small group, a newly qualified police Lieutenant with a sizeable debt to some people his superiors know all about for all the wrong reasons. In a hurry to find the money to pay back her dead husband's creditors, his wife accepts the offer of work from a foreign intelligence agency on top of her civil service secretarial job, delivering the package they gave her to her place of work in exchange for enough money to cover half her husband's debts, with the expectation of more work from the same source in the near future.
The package, as it happened, was not the recording device that she had assumed it to be, but was in fact a canister of nerve gas, which when triggered filled the entire building, killing off an entire treasury department office and allowing the foreign spies, fully kitted out with gasmasks and hazmat suits identical to those used by the local fire brigade to enter the building unchallenged, destroying every computer in the building and setting fire to all hardcopy records until they reached the main safe, which they blew open in the work of a few minutes, stealing crucial government correspondence before exiting the building. One of the office's security guards, who had been taking an unofficial break up on the roof of the office when the nerve gas attack took place intervened as they tried to leave, shooting one of the foreign agents in the leg, forcing his comrades to leave him behind as their cover was blown wide open.
In interrogation, the wounded agent cracked easily, revealing the nation that sent him and the nature of the correspondence his comrades had stolen, resulting in strained international relations with that country that quickly developed into an outright cold war which lasted for another seventy six years...
(Side note, not all worst case scenarios need to end in mutual destruction...)
I dropped all my loose change down a storm drain.