René Benoit, also known as La Grenouille ("the Frog" in French), was a French national and an illegal arms dealer whom Jenny Shepard spent over a decade trying to catch as she believed that he had murdered her father, Colonel Jasper Shepard, and later developed an obsession with capturing him, even recruiting NCIS Special Agent Anthony DiNozzo to go undercover and form a relationship with René's daughter, Dr. Jeanne Benoit.
NCIS Season 4
NCIS Season 5
In the Season 5 premiere episode, Bury Your Dead (episode), it was revealed that Rene Benoit knew about Tony's undercover operation and also about Tony's true identity.
He forced Tony to talk to Jeanne with Tony reluctantly divulging everything which left Jeanne in a state of denial and disbelief.
Hours after his driver, Henri Rousseau had been killed in an explosion, La Grenouille visited Jenny Shepard and admitted that he had paid Jenny's father, Colonel Jasper Shepard to take a bride.
La Grenouille sought protection from his enemies due to the fact that he could also no longer trust Trent Kort but Jenny personally refused the quest out of spite.
At the end of the episode, La Grenouille's body was seen floating in a canal with a single gunshot wound in the center of La Grenouille's forehead.
La Grenouille's remains were later removed from the canal and an autopsy performed on his remains.
Jeanne was interviewed and told that the FBI that she'd seen DiNozzo kill her father.
As such, in Internal Affairs (episode), the entire NCIS Major Case Response Team fell under investigation for the crime with FBI agent Tobias Fornell being given the task of interviewing all the members of the team while NCIS Assistant Director Leon Vance oversaw things.
Upon a further interrogation which Jenny personally conducted, Jeanne admitted that she hadn't witnessed the killing.
Jenny was later suspended from her duties, resulting in Vance becoming the acting Director of NCIS.
CIA agent Trent Kort brought the investigation to a halt by claiming that the agency was responsible for La Grenouille's death in a "sanctioned" action. Gibbs was not convinced, continued investigating, and found forensic evidence suggesting that Director Shepard had been the one who had killed La Grenouille but he buried the evidence. It is proven that La Grenouille's assassin used Director Shepard's gun to kill him. Shepard, however, claimed that La Grenouille took the gun when he left her home.
While Kort confesses to murdering La Grenouille, it is further suggested that Shepard herself killed La Grenouille when Gibbs remembers that he saw La Grenouille put her gun on the table before he left.
In Judgment Day Part 1 (episode), after receiving the file from Fornell, Gibbs examined the evidence once again and after glancing at a single bullet later discovered that the bullet which had a mark on it was a match to shell casings found at the crime scene, confirming his theory that it had been Jenny, not Kort who had killed the Frog.