"NCIS" celebrated its milestone 300th episode by featuring the MusicCorps Band, a part of a music rehabilitation program for wounded veterans at Walter Reed Hospital in Washington, D.C.

But first, we're in Iraq where Petty Officer Elaine Dodd and her husband Spencer are killed on a personal visit to Iraq, where her husband is doing research for a novel.

The report is that the sniper filed from a mile away, which means he had access to a weapon more advanced than anything that had previously been seen. The concern is that Americans are in a whole new kind of danger.

When Abby gets the bullet fragments from the Dodds' bodies, she discovers that they were armor-piercing bullets produced for the U.S. Army.

In further investigating, the NCIS team discovers that two months prior, there was a firefight just two miles west of where the Dodds were killed. It was where a unit of Special Ops Marines was testing a new weapon: an XR-30, which takes the guesswork out of shooting a moving target up to 2,000 meters. Only Marine Gunnery Sergeant Aaron Davis survived and he is at Walter Reed Hospital recovering.

Gibbs' shrink Grace, who is based at Walter Reed, tells Gibbs that Davis is struggling and therapy isn't working. He's completely shut down. She thinks that Gibbs can connect with him sniper to sniper. It is Gibbs' best shot at getting the info he needs on the firefight that wiped out Davis' unit.

Gibbs approaches Davis, who tells him he can't help and throws him out of his room. Gibbs reminds himself that snipers are patient and stubborn and he sits down to wait out Davis.

Bishop and McGee enlist Davis' 16-year-old daughter's help. She says she is a detail person – her father taught her – so she puts together a list of information on her dad to help the NCIS team. She says he used to be happiest when he was singing.

This is where MusiCorps comes in. Davis has been going to the band room every day for three weeks but has yet to participate.

DiNozzo tells McGee and Bishop that Spencer Dodd's passport was swiped at Dulles International the day after his death, which turns out to be the motive for his assassination. Abby checks the airport security video, but the fake Dodd was like Houdini and magically managed to avoid the cameras. She does get the number of the cab he got into and she tracks that down.

DiNozzo and McGee go to the Drake Motel, where the cab dropped fake Dodd off, but he is gone. There is an empty box under the bed. The package was sent from Baghdad and it looks like it contained a gun. They discover fingerprints, but there is no match in the system. Abby does find some numbers on the shipping box and works on those.

Gibbs is still waiting at Walter Reed to talk to Davis. Davis finally relents and talks to Gibbs, who is tired, and explains to Davis that he sleeps on the couch at home because he feels funny in the bedroom since his wife died. But a spring broke, so he hasn't been sleeping well.

They bond over sniper talk.

Davis opens up and tells Gibbs about the attack. There were a half dozen insurgents approaching, but what wiped out his unit was an RPG strike. When Davis came to, the enemy was gone. Davis thought the weapons had been destroyed along with his unit.

Abby and Gibbs figure out from something Davis said that there might be a video of the firefight, which didn't get posted because the insurgents couldn't get back to get the camera.

Davis leaves the hospital. McGee pings his phone and Gibbs finds him in a truck with a gun, contemplating suicide because he doesn't want his daughter to see him like he is. Gibbs tells Davis how much he means to Riley. She talked to his agents all day about him. Gibbs says, "When she looks at you, all she sees is her dad. You need help Gunny. Say you will take it."

Grace tells Gibbs that whatever he did or said to Davis, it worked. He's accepted help.

The troops in Iraq find the camera, which has an image of the fake Dodd. Facial recognition discovers he is a former sniper with the British SAS named Matthew Cross, who spent several years in Iraq as a boy in the aftermath of the Gulf War. He blames the "oppressors" for the state of the country.

Abby realizes the numbers on the box are airport radio frequencies, specifically Lafayette Field in Virginia. Gibbs heads out to search for Cross, but as a sniper rather than an NCIS agent.

The team figures out that the target is a plane belonging to Lamar Cresset, an oil bigwig. Also on board is Anwaar Bashaarat, who works under the Saudi oil minister. Their death at the hands of an American weapon would get an international reaction.

Just as Cross is going to take down the plane, Gibbs, hidden by his ghillie suit, goes sniper on the sniper and kills him.

Gibbs goes to see Davis and tells him the XR-30 has been recovered and the sniper is dead.

We close the show with Taye Diggs, who played Davis, performing Leonard Cohen's "Hallelujah" with the MusicCorps Band; as Gibbs heads into his bedroom for the first time in years to sleep. There is healing for both of them.