One is a pioneering fighter pilot, another is a decorated intelligence agent and the third is a celebrated film director. Right now, all three are sitting in Russian jails.
The cases are not directly related, but all three are citizens of neighboring countries in conflict with Russia. Two are from Ukraine, arrested after Russia's annexation of Crimea and the war with Russian-backed separatists in Ukraine's eastern provinces. The third is from the Baltic nation of Estonia.
All are being held on what critics in the West say are questionable charges, and collectively, the cases reflect the worsening relations between Russia and a number of countries that used to be part of the Soviet Union.
Here are their stories:
Nadezhda Savchenko: Savchenko, 33, is a first lieutenant in the Ukrainian armed forces.
She is being held in solitary confinement at a prison in Moscow and has been on a hunger strike that began Dec. 13 and is now more than a month old.
Savchenko volunteered last year to join the Aidar Battalion, fighting Russian-backed separatists in eastern Ukraine.
Ukrainian military officials say she was captured by the separatists on June 18 of last year. Video of her interrogation, apparently by separatists, was posted on June 19.
The Ukrainians say the separatists handed Savchenko over to Russian authorities, who transported her from Luhansk to the southern Russian city of Voronezh no later than July 8. That story would seem to be supported by the earlier video, which shows her in captivity wearing military fatigues.
But Russian prosecutors say Savchenko was apprehended in Russia, wearing civilian clothes and posing as a refugee.
Savchenko is charged with complicity in the deaths of two Russian journalists, who were killed in a mortar attack at a checkpoint in Luhansk on June 17. The charge says that Savchenko acted as a spotter and directed the mortar fire at the journalists, knowing that they were civilians.
Savchenko's Russian defense attorney says phone records prove that she was nowhere near the scene at the time of the deaths.
Savchenko is a high-profile prize for the Russian authorities.
She's famous in Ukraine for breaking down barriers for women serving in the military. She completed rigorous paratrooper training and served as the only female member of Ukraine's military forces in Iraq.
When she returned, Savchenko became one of the first women to train as a military pilot in Ukraine, flying an advanced bomber and an attack helicopter.
While she was in prison, Ukraine's Fatherland Party put her up as a member of parliament and she was elected. She has since been named a delegate to the Parliamentary Assembly of the Council of Europe (PACE).
Savchenko's attorney says she has vowed to continue her hunger strike until Russia releases her or she dies in captivity.
Eston Kohver: Kohver, 43, an officer in KaPo, the Estonian Internal Security Service, is being held in a high-security prison in Moscow on charges of spying.
Russian authorities say Kohver was caught in the Russian region of Pskov, close to the Estonian border, carrying a U.S.-made Taurus handgun, audio recording equipment and 5,000 Euros (about $6,000) in cash.
Estonian officials say their man was actually abducted by Russian commandos in a raid on Estonian soil.
Kohver was reportedly waiting to meet an informant near a remote checkpoint on the Estonian side of the Russian frontier.
The Estonians say the Russians jammed their communications and fired smoke grenades to hide their moves from Kohver's back-up team. They say Russian special operations forces overpowered Kohver and dragged him across the border and into Russia.
The Estonian and Russian border guards conducted a joint investigation of the incident, and the Russians confirmed that an incursion onto Estonian soil had taken place.
However, Russian courts went ahead and extended Kohver's confinement, most recently until April 5. Late last month, an Estonian doctor was allowed to visit the jailed agent, and pronounced him to be in satisfactory health.
Kohver's capture has strong symbolic value for Russia, because it came just a day after President Obama visited Estonia and promised that NATO would protect the small Baltic nation from any aggression.
Oleg Sentsov: The 38-year-old Ukrainian filmmaker is being held in the same Moscow prison as Kohver.
Along with three other Ukrainian men, he's accused of plotting terrorist acts, including blowing up buildings, utilities and monuments in the Crimean cities of Simferopol, Yalta and Sevastopol.
The men were arrested in early May, less than two months after Russia annexed Crimea from Ukraine.
Sentsov had been active in the protests that ousted former Ukrainian President Viktor Yanukovych nearly a year ago.
He also aided Ukrainian soldiers stationed in Crimea by giving them food when they were surrounded by Russian troops.
Russian prosecutors have accused him of being associated with the Ukrainian nationalist group Right Sector, a claim that both he and Right Sector deny.
Sentsov also denies plotting terrorist acts. His attorneys say the case against him is based solely on the testimony of some of his co-defendants, and they say that testimony was likely obtained under torture.
Sentsov himself says that he was beaten and threatened with rape and murder by interrogators who tried to force a confession from him.
His case has drawn support from high-profile filmmakers, including Pedro Almodovar, Ken Loach and Wim Wenders.
He made a name for himself with some highly regarded short films, then made his feature debut in 2012 with a film called Gaamer, about a computer-game champion who finds that his obsession is cutting him off from real life.
Sentsov, a single father of two, faces up to 20 years in prison if he's convicted.