Sierra Bauer, an aircraft mechanic, aids Alice Holmgren during her collapse at the airport. Alice's ICD (implanted cardiac device), made by Voyageur Cardiac Systems (VCS), fails catastrophically.
Alice's daughter, a VCS employee, questions the ICD failure. She shows Sierra an internal report, not shared with FDA, on device malfunctions.
Musician Matt Lanier witnesses his mentor, conductor Magnus Danilson, collapse and die during a concert, due to the unexplained failure of his Voyageur ICD. Matt, suspicious, confronts Justin Biggs, a talented but widely disliked Voyageur programmer, who hints at a cover-up but provides no proof.
Faced with threats, both internal and external, VCS CEO Stephen Hartsburg hires two investigators, attorney Pen Wilkinson and hacker Weezy Napolitani, to investigate the device failures. He fails to disclose that he is being blackmailed by unknown persons demanding public revelation of the defects, and hinting that further device failures may be forthcoming. Hartsburg secretly hires slippery international fixer Henri Hawke to negotiate with the blackmailer. Pen meets Weezy, who uncovers extra code inserted into ICD updates, suggesting tampering (a "kill code").
Pen and Weezy join Sierra and Matt to investigate the deaths. The collective identifies former VCS programmer Ralph Calder as a suspect. Calder's wife died from an ICD failure he blames on Voyageur. To exact revenge and force reforms, Calder may have modified patient ICD receivers into transmitters to activate the kill code, inducing failures.
Hawke brokers a deal between Calder and Hartsburg, meeting Calder's demand to form a watchdog foundation to police medical devices. The funding will purportedly be provided by Gina Apate, a shadowy foreign financier and former intelligence operative. She makes an agreement with Hawke to extract a settlement from Hartsburg to finance the watchdog foundation and split the proceeds. But Apate double-crosses Hawke and Hartsburg, appropriating all the funding and attempting to exploit VCS's problems to take over the company and weaponize its technology.
The collective splits up: Sierra and Matt stake out Calder's cabin, while Pen and Weezy investigate Hawk and Apate and hack the VCS database to search for vulnerable patients. At Calder's cabin, Sierra, Matt, and Quinn confront Biggs and his thugs. A standoff ensues. Biggs escapes with the transmitter, but the group captures Calder. He confesses partial involvement but implicates Apate.
The collective meets again. They have discovered Reverend Leighton's vulnerability and Apate's use of Tricia Doran as a hostage. Tricia flees Hartsburg's lake home, making a run for the airport. Apate's thugs pursue. The group realizes that Biggs and Apate, armed with Calder's transmitter, will try to kill Reverend Leighton to eliminate his opposition.
Pen and Weezy thwart Biggs's attempt on Leighton, intercepting and ramming his vehicle. Police intervene, killing Biggs. At the airport, Sierra, Quinn, and Matt rescue Tricia from Apate's men in a shootout. Quinn sustains a minor wound but prevails.
Hawke confronts Apate and Hartsburg at the latter's lake home. Apate kills Hartsburg. Hawke shoots Apate in self-defense, staging it as murder-suicide. He funds Calder's watchdog foundation anonymously.
The FDA recalls the defective devices. Voyageur, facing investigations and possible bankruptcy, reorganizes under Reverend Leighton's leadership. The group reflects on losses: Alice, Danilson, Lois Calder. They part ways, changed by the ordeal. Calder faces justice; the watchdog foundation endures. (690 words)
