Oct. 25, 1955: John Anthony Walker Jr. joins U.S. Navy.

Sometime in 1968: John Walker begins spying for the Soviets.

Spring 1968: Barbara Walker finds items in her husband's desk leading her to conclude that he is a spy. John Walker later tells his wife that he has passed information to the Soviets.

1969: Barbara Walker accompanies her husband as he drops off a bag filled with documents in the Washington area.

Sometime between 1970 and 1975: John Walker allegedly recruits close friend Jerry Alfred Whitworth as a spy.

1971: Barbara Walker accompanies her husband on a second "dead drop" in the Washington area; he picks up a bag containing $35,000.

July 1976: John Walker retires from the Navy.

October 1979: John Walker's daughter, Laura Walker Synder, plans to leave the Army. John Walker urges her not to resign, saying she could make a lot of money by providing him with classified information. She turns him down.

January 1980: John Walker urges his brother Arthur, a retired Navy officer, to get a job where he would have access to classified information.

Feb. 25, 1980: Arthur Walker begins working as an engineer for VSE Corp. of Chesapeake, Va., a military contractor.

Sept. 2, 1981: Arthur Walker photographs a confidential document at John Walker's office.

February 1982: John Walker visits Laura Snyder, urges her to re-enlist and says she could receive $500 to $1,000 a month in exchange for classified information. John Walker later sends her $500 as an "advance." She does not re-enlist.

April 28, 1982: Arthur Walker gives a confidential document from VSE Corp. to John Walker. During this period, John Walker gives him $12,000.

Dec. 13, 1982: Michael Lance Walker, John Walker's son, joins U.S. Navy.

Summer 1983: John Walker tells Michael, who is assigned to a fighter squadron, he will pay Michael if he provides him with classified material.

November or December 1983: Michael Walker gives his father a classified document from a "burn bag" of documents to be destroyed, the first of about six documents he gives his father before he is transferred to the aircraft carrier USS Nimitz.

March or April 1984: John Walker gives Michael Walker $1,000. October 1984: Michael begins taking classified documents from the burn bag aboard the Nimitz. On about 10 occasions until the ship leaves Norfolk, Michael gives his father stacks of documents.

Nov. 23, 1984: Barbara Walker telephones the FBI to pass along a tip that her ex-husband is a spy.

May 19, 1985: Agents follow John Walker from Norfolk to Montgomery County. Agents searching a wooded site in rural Poolesville discover a bag, disguised as trash, filled with classified documents from the USS Nimitz and letters from Walker to his Soviet contact.

May 20: John Walker is arrested.

May 22: Michael Walker is arrested.

May 29: Arthur Walker is arrested. Late May: Prosecutors and lawyers for John and Michael Walker open plea negotiations.

Sometime in June: John Walker has "limited debriefing" sessions with FBI agents and prosecutors.

June 3: Jerry Whitworth is arrested.

June 25: A draft plea agreement is drawn up. Aug. 9: A federal judge in Norfolk finds Arthur Walker guilty of seven counts of espionage.

Week of Oct. 20: Defense lawyer Fred Warren Bennett receives a call saying the basics of the plea agreement are accepted.

Oct. 28: John and Michael Walker plead guilty in federal court.