During a training exercise, several Marines are injured in a friendly-fire accident. Lieutenant Williams, the officer who called in the artillery strike turns out to be the son of General Williams, a former Commandant of the Marine Corps and Medal of Honor recipient, and despite being otherwise entirely devoid of personal integrity, has claimed responsibility for the mishap, having been drunk while calling in the strike. When one of the injured Marines dies, and Williams is informed that he will be charged with Manslaughter, he rescinds his previous statement and places the blame on another officer, Lieutenant Boone, who he claims transposed two digits while relaying the call for an artillery strike. Harm is particularly suspicious because the tape used to record the radio calls in the exercise first goes missing then turns up with some audio abnormalities on it.
"Desert Son" contains examples of the following tropes:
- A Father to His Men: Williams and Boone are both presented as different versions of this. Lt. Boone takes time to visit the injured Marines in the hospital, and when the evidence suggests that it was his mistake that lead to the friendly fire incident, does nothing to avoid the blame. Williams meanwhile is a subversion, going out of his way to be friendly with his men, partying with them and buying them drinks, but quick to shirk responsibility when a mistake on his part gets one of them killed.
- The Cameo: Former Lieutenant Colonel Oliver North of Iran-Contra fame as Meg Austin's "Uncle Ollie", who she calls in for a favor. Heavily implied to be cast As Himself.
- Cigar Chomper: Captain Reed.
- Determinator: General Williams made three trips in a damaged helicopter to rescue a special operations team, after having most of his leg blown off and the rest of his crew killed. That's why he got the Medal of Honor.
- Drinking on Duty: Lt. Williams jokes that he's not hungover, but rather "still drunk" just before the friendly fire incident, and later claims his hangover to have caused his mistake, before changing his story and letting Boone take the blame.
- Famous Last Words: "Why me?" Harm tells the general that his son's last words were an admission of responsibility for what he'd done.
- I Am Spartacus: Lampshaded. Harm and Reed get into a fist fight. Later, General Butler demands to know who started it. In unison, both men declare "I did!" General Butler is not impressed, and demands that someone explain to him what happened.
- I Knew It!: Captain Reed's reaction after Harm proves that the tape was tampered with.
- Jurisdiction Friction: Captain Reed does not like Harm interfering in his unit's training with their investigation, especially as he sees it as open and shut. This leads directly to Poor Communication Kills.
- Kick the Dog: Lt. Williams shoots Boone when confronted with the proof of what he's done, then shoots the radio so the heroes will have to drive Boone back to the camp to get medical assistance rather than try to chase him.
- Laser-Guided Karma: Lt. Williams' fate, accidentally killed by an artillery strike fired by the same battery he was spotting for when the accident happened.
- Let's Get Dangerous!: Captain Reed lights up his cigar just before ordering his artillery battery to fire.
- Like a Son to Me: General Williams to Lt. Boone, the only friend of Lt. Williams that he approves of.
- Manipulative Editing: Lt. Williams has a female DJ (who has a crush on him) edit a tape recording of a radio conversation to make it sound like Lt. Boone transposed a set of numbers, when in fact Boone had perfectly relayed the incorrect coordinates Williams had sent him. Harm picks up on the editing because there's an analog hiss on the edited portion due to the DJ's different equipment.
- Never My Fault: Lt. Williams is incapable of taking responsibility for his own actions. His dying words are "Why me?", unable to accept that everything that has happened to him has been his own doing.
- Old Soldier: Captain Reed served in the enlisted ranks before bucking for officer. As a result, he's unusually old and salty for a Marine Captain. And of course there is General Williams.
- Operation: Jealousy: Minor example. Uncle Ollie is concerned that by making Harm stay in the humvee while she meets with Ollie, Meg might give the wrong impression that Ollie is her boyfriend. Meg grins and replies "That's the idea."
- Poor Communication Kills: Harm and Captain Reed do not get along, and Reed gives the bare minimum of assistance when Harm and Meg go to investigate the accident site. This plus one knocked over road sign nearly get Meg and Harm killed when they accidentally enter the Free Fire Zone.
- Reasonable Authority Figure: General Williams insists that Harm be impartial in the investigation, rather than covering up for his son's failure like many others have done. Major General Butler similarly makes it clear that he expects his men to cooperate with Harm's investigation. Captain Reed doesn't like Harm at all, and he's very harsh towards Lt. Williams (and rightfully so), but when it seems that Lt. Boone was responsible, he simply tells him that mistakes sometimes happen, and he should learn from it rather than let it haunt him.
- Retired Badass: General Williams, former Commandant of the Marine Corps and Medal of Honor recipient. Even as a retiree, he still warrants his own helicopter transport and honor guard.
- Road Sign Reversal: A sign marking an entrance into the Free Fire Zone has been knocked down, which nearly gets Harm and Meg killed.
- Run for the Border: Lt. Williams tries to run for Mexico, by crossing through the Free Fire Zone.
- Target Spotter: Williams had this role in the exercise. Because he was wasted out of his mind, he gets the coordinates mixed up.
- The Unfavorite: Lt. Williams. He claims that his father elevates his deceased older brother to unreachable heights as a paragon of virtue, making it that much worse.
- "Well Done, Son!" Guy: Lieutenant Williams feels that his father has always considered him a failure. What's worse, is he's right, and his father's opinion of him is well-founded.
- Wham Line: After Boone has been found to blame for the mishap, Williams is out spotting for artillery strikes again, and remarks that he never knew how much better he'd be at spotting artillery simply by doing it while sober. The corporal riding in the humvee with him is stricken speechless by the implications of this remark.
- What the Hell, Hero?: Major General Butler gives Harm and Reed an ass-chewing of epic proportions after the two get into a brawl. He only gets angrier when both men try to claim responsibility at the same time before Meg explains that it was the result of a particularly bad misunderstanding.
- Unfriendly Fire: What prompted the investigation - marine artillery hitting marine infantrymen during a training exercise.
As you were...