Sam and Rountree are training for a triathlon and Callen mocks them. Kilbride tells Deeks he's considering sending him to the NCIS Western Conference in Costa Rica. The team is assigned to investigate arson at Global West Ventures Corp., a naval defense contractor. The scene was signed by Randall Perez, the arsonist known as On Alert, who attacks companies that have committed environmental crimes. The building's renovation foreman was found dead inside. The agent in charge of the FBI's On Alert task force, Summer Morehurst, is Rountree's ex. Kilbride surprisingly gives Callen a folder on Pembrook. Fatima overhears Rountree and Summer squabbling. Sam suspects that someone other than Perez may have set the fire. Summer and Rountree question Perez's daughter Crystal and sister Denise. Crystal admits Perez had been in touch with her. The arsonist used thermite. Sam determines the arsonist was picked up by an accomplice, whereas Perez always worked alone, so the arsonist is likely a copycat. Denise meets up with Perez. Summer arrests her but Perez gets away. Sam and Deeks find a storage locker where the thermite is being produced. Kilbride reports that Perez's accomplice may be Martin Navarro. He also sends the address to where he had tracked Perez's burner phone. When arrested, Perez claims Navarro is the arsonist. Perez had left some of his supplies with Navarro. Crystal also knew Navarro. Fatima figures out that all the companies on Navarro's target list supported Sen. Garrett, who killed a major environmental bill. Navarro and Crystal are targeting Garrett. Navarro shoots Garrett's aide in the leg while Sam and Deeks track Crystal. Rountree captures Navarro. When cornered, Crystal threatens to light herself on fire. But Summer talks her into surrendering. Deeks declines the chance to attend the conference. Kilbride defends Hetty's past actions to Callen.