Together, Gwendolyn and Kendall Myers set out to give the second half of their lives new meaning. At first, disillusioned with the pace of change in Washington, the great-grandson of Alexander Graham Bell, who at the time was a State Department contract employee, and the housewife turned political activist moved to South Dakota, where they embraced a counterculture lifestyle, even growing marijuana in the basement. They marched for legalized abortion, promoted solar energy, and repaired relations with six children from previous marriages.

When the wide-open spaces of the West quickly grew too small, the couple returned to Washington a year later, renewing their ties to the establishment that they had rejected.

But the government says the real reason for the Myerses’ 1980 return was to spy for Cuba. In a complaint that reads in parts like a novel, federal prosecutors allege that Mr. Myers, now 72, used his top-secret clearance as a State Department analyst to steal classified information from government files for nearly three decades, and that Ms. Myers, 71, who worked as a bank clerk, helped pass the information to Cuban handlers. They were arrested earlier this month and are being held without bail.