A retired Navy officer kills himself and leaves a note for NCIS. The dead man is Retired Navy Master Chief Arturo "Art" Amador. Marie Stanhope, the National History and Heritage Command deputy director, shows up to visit Art. She had received a note from Art, along with an extremely rare, valuable coin that he wanted to donate to the Navy Museum, where he had volunteered. Art's donation would help the museum overcome its budget shortfall. Stanhope can't accept it without knowing its provenance. GIbbs calls in historian Ducky. Ducky encourages them to picture themselves in another time as they go through Art's files. Art had an inoperable brain tumor. Bishop finds a letter from Annie Downing, the love of Art's life. Annie's father, who had the coin, refused to approve their relationship. Spencer, Annie's brother, arrives at Art's garage and said the coin was stolen from his family 50 years ago. Spencer's printing-press business is failing and the coin could help with its debt. Art had the coin in his pocket when police rousted him for a domestic disturbance. Palmer determines Annie Downing was poisoned. No one believes that Art was a thief or a killer. Annie's body gets exhumed and she's wearing the engagement ring her father threw in the fireplace. Annie was poisoned with thallium by someone nearby and Art was serving in Vietnam. Her father gave her back Art's ring at her sickbed. McGee proves that Spencer has been embezzling money from his company. The stamps Annie used on her love letters were poisoned by Spencer and had his DNA on them as well. Aunt Bertha said Annie stole the coin originally, but Art returned it. Then Bertha gave it to him as a momento of Annie. So the coin ended up going to the museum.