Sprocket and her brother Silver Nitrate are a pair of criminals with a theatrical focus. When first introduced, Silver and Sprocket were operating out of the Lyric Theater downtown where they created a fake copy of a long-lost black and white Captain Video television show that was Vitamin Flintheart’s first film role. Silver seemed to generally be the front of the criminal enterprise while the barefooted Sprocket played it cool and supported her brother when needed. Vitamin and his stage co-star Mary Perkins visited the Nitrates to watch a small portion of the video. Silver then asked for $300,000 to finish restoration of the film.
Vitamin left to consider the offer and a shady actor named Miles Mycroft came to the Lyric to meet with Silver and Sprocket. Miles played Vitamin’s role in the fake film and wanted to be paid. Silver instead strangles him and feeds him to the Nitrate’s pet hyena Lena. This would be the start of their undoing as Mary Perkins had recognized Miles as Vitamin and asks Dick Tracy to help Vitamin with the scam. When confronted, Vitamin reveals he knew all along it was a con as he actually played the role of a monster and not a video ranger.
Dick and Sam Catchem approached the Nitrates at the Lyric to ask them about Miles Mycroft and the authenticity of their films. Silver didn’t admit to knowing Miles and claims all his videos are legit to his knowledge. Tracy leaves, knowing otherwise but still gathering information and he and Sam find Silver’s bloody jacket from the Mycroft murder in a garbage bin.
The Nitrates meanwhile were feeling the heat and decided to blow town without the money. They head to the train station where the Silver Zephyr was about to leave station, but the Zephyr was a misdirection and they soon double-back for their car at the Cars of the World Museum.
Their car is in fact the famous Flattop Jr. car, completely restored since its destruction many years ago and modified to include air horn machine guns. The Nitrates nearly escaped cleanly in the famous car, but Lizz was on their trail to the train station and while waiting for a train she also stopped at the Cars of the World Museum and asked about the missing vehicle. She put two and two together when one of the owners matched the description of the perpetually barefooted Sprocket Nitrate.
The chase is soon on with Sprocket driving (Silver doesn’t know how) and Sam and Dick soon tail the Nitrates. The brother-sister duo deploy caltrops which flip Sam and Dick off the road. They then ram through a police roadblock, firing the machine guns in their air horns the whole time. Sam and Dick quickly acquire another vehicle and begin a local grid search while the Nitrates hide out in a barn in a throwback to the Flattop Jr. / Joe Period hideout.
Lena escapes briefly and Silver goes to fetch her, giving him advance warning of Catchem and Tracy’s police vehicle. The Nitrates quickly jump back into their car and burst from the barn, racing towards a lake. Sprocket is upset at this point, blaming her brother for this whole mess which they didn’t even make money on. Silver smacks her hard and she fumes and drives straight into an ice-covered lake. The car crashes through the ice and sinks to the bottom, with Silver in a panic. Sprocket calmly explains the car is air tight and can survive this and informs Silver with a hint of danger in her voice that he’ll never hit her again. The police send divers into the lake but the Nitrates are gone.