The story takes place immediately after Card of Ten, following the remaining members of the away team in anti-matter Pelvanida. An extended flashback takes place at the same time as Darwin's Soldiers (Furtopia).
After the bridge shuts down, Hawkeye prepares to escape Pelvanida with passengers Neku and Snow (anti-matter), when Kagetora teleports onto the shutte with Vic in tow. they escape and fly into Las Vegas to find it similarly irradiated.
They reach Crimson Base and Neku risks his life to get them all chemsuits. They continue on and eventually pick up a life sign. Kagetora, Vic, and Neku explore the nearby buildings and Neku springs a spiked pit trap. While attempting to save them, Kagetora is confronted by a water bear named Tardigan.
Tardigan explains that he was trying to kill them because he assumed they were government agents; he was getting revenge for what happened to his home city. He admits he's not sure what exactly happened. They return to the Hawkeye, where the team decides to stay the night in Tardigan's factory.
That night, Tardigan kidnaps Snow. Neku and Kagetora set out into the city to rescue her while Vic tries to reach Hawkeye. The city turns out to be loaded with unnumerable deadly booby traps and only Vic succeeds in his goal.
However, Snow wakes up in a science lab and manages to free herself. Recognizing the building's function, she contacts Vic and gets the Hawkeye to arrive just in time to rescue Neku from death at Tardigan's hands. While the shuttle flies away, Tardigan hooks them with a grappling hook, but Kagetora jumps on the rapelling water bear and detonates his explosive, killing himself and sending Tardigan tumbling to an uncertain fate.
The shuttle attempts to rereach Pelvanida but must land early for repairs. While landed, two chemsuited individuals approach the ship. They introduce themselves as Ender McThair and Ken, Pelvanida personnel who survived the destruction. They bring Snow and Neku back to their hideout in the Robinson family's cellar, where to their surprise they meet James Zanasiu. He explains how they came to be here.
During a terrorist assault on Pelvanida, James and his two allies are in a standoff against better armed terrorists outside their lab. The lead terrorist demands their names; while James and Ender complies, Ken claims his name is Amos Day. Nevertheless, James is who they're looking for, and Leither brings the three to the Presentation hall where James meets Ashley, the terrorist leader.
To explain why she's interested in him, Ashley tells James her backstory: she lived on the streets of matter universe Carson City with her twin brother Halsey. After attempting to kill a rabbit at Hidden Meadows, she was kidnapped by Pelvanida personnel and experimented on. She gained the ability to transport from her universe to the anti-matter universe, and this whole terrorist invasion is an attempt by Halsey to return his sister to her proper universe. Because James' name is on matter universe rosters, Ashley wants to know how he teleported over.
When he proves to be completely clueless, she takes him, Ender, Ken, Leither, and a burly terrorist to Luddly's lab so that his canary experiment can reveal James' most emotional moment. When she accidentally kills the bird, chaos breaks out, and Ender and Ken escape.
Ashley takes James to the sublevels where they witness the Einstein-Rosen bridge activate for the first time. All the terrorists follow Ashley to the event horizon, but James hesitates. This proves to save his life when a rocket from the other side kills everyone in the room.
Neku and Snow admit that Ashley was wrong; there is a completely different James Zanasiu in their universe, so he is not from another universe. This crushes James, but as a group they decide this is their best chance to escape the quarantine zone. They must kill Tardigan, otherwise the border patrol will shoot them on sight.
The next day, the team flies Hawkeye to Crimson Base and Vic prepares to reactivate Neku's and Snow's powers. Tardigan attempts to sabotage their procedure, and split the team up in the process.
James and Ken find themselves in the bowels of the maintenance sectors. They stumble across an area where the machinery has been reactivated and locate a prototype bio-bomb ready to fire. If they don't deactivate it, Tardigan will launch it out of the quarantine zone and thousands more people will die. James climbs into the pneumatic tube and wraps the bomb in his chemsuit, intent on sacrificing himself for the greater good, but to his horror Ken removes his suit so that James won't die.
Meanwhile, Neku and Snow fight Tardigan, with their powers reactivated, and soundly defeat him. Snow learns that Tardigan simply wanted to die, and built the booby-traps to use on himself, despite none of them working.
Everyone meets at the shuttlecraft and finds that Tardigan killed the AI Hawkeye. Nevertheless, Vic and Ender make the ship flyable and with Neku powering it they fly over the quarantine wall.
The story ends with the survivors celebrating their escape, only to be cut off by a knocking on the shuttle door.
Flashback only characters
- This story surpassed Card of Ten for the longest story taken to be posted. All in all it took over 10 months, while Card of Ten took 8½.
- This story is only a few pages shorter than Ship of State, and therefore the third longest story in the canon.
- LettuceBacon&Tomato originally planned for Tardigan to be the only character created specifically for the story, but eventually added a few more characters to the flashback for explanatory purposes.
- The title is a reference to the detonation term 'ground zero,' referring to the location where an explosive detonates. This story takes place in a city right next to a bomb epicenter.
- Only half of the main characters in this story survive, tying this story with Nietzsche's Soldiers and Fool's Gold for lowest survival rate. It also has the most main characters of the three stories.
- This story makes heavy use of the 'frame narrative', where nested stories are told to characters of the larger narratives. All in all, three stories (Neku's, James', and Ashley's) are nested in each other at one point.