When Fletcher and Skylar go missing, the gang starts to panic. They all disappear one by one, until only Oliver, Angus, Olive, Bree, and Kaz remain. Oliver and Douglas team up to find them, but then Oliver runs into Chase, actually a dangerous android named Troy 2, who takes him away. Douglas and the remaining heroes set out to get help from Leo and an insane Adam-who's been infected by the deadliest virus ever made by Gao-Ricardo, the new android successor to Ricardo, Gao, and Gao-Krane who has both Gao's brain and Ricardo's and possessed by Krane's soul-to rescue their friends. But what exactly is the secret origin of Adam's virus?
- Jake Short as Oliver Quimby/ Fletcher Quimby
- China Anne McClain as Chyna Parks
- Bradley Steven Perry as Kaz Duncan
- Sierra McCormick as Olive Doyle
- Paris Berelc as Skylar Storm
- Kelli Berglund as Bree Davenport
- William Brent as Chase Davenport
- Aedin Mincks as Angus Chestnut
- Chase McFly as Jesse McFly
- Leo Howard as Troy 2/ Ricardo (before Troy 2's arrival)
- William Brent as Troy 2 disguised as Chase
- Ping Wu as the voice of Gao-Ricardo
- Mateus Ward as Ricardo (after Troy 2's unmasking)
- Jeremy Kent Jackson as Douglas Davenport
- Tyrel Jackson Williams as Leo Dooley
- Spencer Boldman as Adam Davenport
- Graham Shiels as the voice of Adam Davenport infected with the virus
- The title is a reference to the book And Then There Were None.
- Adam's bionic chip is infected by a strange cross of the Triton App and the Trojan App, which contains Krane's soul in a final attempt to return to form.
- There's a novelization of this ep.
- New co-writer\director Duggie Davenport joined the staff of this episode.
- This episode was dedicated to Duggie Davenport's first birthday as an adult and his first birthday with the show.
- The Ricardo-Krane paradox implies that Ricardo built a new body for himself in the style of Gao, on Krane's insistence. Ricardo is still pure evil after Krane brought him back. He summoned Gao's soul to possess Chase, and it was him who gave Adam the virus.
- Douglas fights for the first time since his fatal injury more than a year before. He has sensory glasses that enable him to hear, smell, taste, and feel more than regular humans, so he can blast people.
- This is the second time in the franchise Adam has been referred to as a dog.
- It is also the second reference to And Then There Were None.