On the evening of July 22, a string of revealing text messages and phone calls circulated between Cuba, Sweden and Spain and back to Cuba — where Oswaldo Payá, one of the country’s bravest and most influential dissidents, was lying dead on a rural highway. That, anyway, is the story of Regis Iglesias Ramírez, an associate of Payá and former political prisoner who says he is determined to expose what he believes was a state-sponsored murder.

Iglesias, who was released into exile in Madrid two years ago and visited Washington last week, said he was contacted that evening by a Spanish Christian activist named Cayetano Muriel, who in turn had been called by Annika Rigo, a Swede who heads the Christian Democratic International Center in Stockholm. Iglesias says he was told that Rigo had received a text message from Cuba saying that a young Swedish Christian Democratic activist, Jens Aron Modig, had been in a terrible accident: A car in which he was riding had been followed and forced off the road by another vehicle. The text said three people from the car had been transported to a hospital, and one was missing.

Modig and a youth leader from Spain’s ruling Popular Party, Angel Carromero, had traveled to Cuba to make contact with Payá, leader of Cuba’s Christian Liberation Movement and the author of a groundbreaking 2002 petition seeking a popular referendum on the introduction of democratic freedoms. So Iglesias says he first texted and then called Payá’s wife, Ofelia Acevedo, who was in Havana, to see if she had heard anything.

Payá’s family knew nothing. But soon afterward came the terrible news from Cuban authorities: Payá and another dissident, Harold Cepero, were dead; and Carromero, who was driving the rented Hyundai sedan they were riding in along with Modig, was accused of causing a one-car accident.

Two months later, that remains the official story. Carromero appeared on Cuban state television, where he confessed to losing control of the car and hitting a tree. He also urged that international attention focus on “getting me out of here.” He faces trial on charges of negligent homicide. [On Monday, the government said the trial would begin Oct. 5 in Bayamo.]

Modig was held incommunicado for five days in Havana, then allowed to return home, where he has remained mostly silent. His spare communications, delivered before leaving Havana and in Stockholm, contain two salient points: He claims not to remember what happened in the crash; and he is worried about Carromero.

As far as Iglesias and other members of Payá’s movement are concerned, it’s quite clear what this adds up to. The accident, they say, was likely caused by Cuban state security, which has managed to silence the survivors by holding the 27-year-old Spaniard as a de facto hostage. The Spanish government, argue the dissidents, is content to tolerate this travesty for two reasons: It wants to free its well-connected activist, who is facing 10 years in prison; and it wants to avoid the diplomatic uproar that would necessarily ensue if it were acknowledged that Payá — a recipient of the European Union’s Andrei Sakharov human rights prize — had been killed by the regime.

The activists claim there is more evidence of foul play than the July 22 text messages. Iglesias says friends of the Payá family traveled to the hospital where the victims of the accident were taken on July 22. There they allegedly encountered Carromero, who repeated that he had been hit from behind and forced off the road by a red Lada sedan. A local police officer read them testimony from two local witnesses who said they saw the Lada at the scene of the accident. According to Iglesias, the Payá friends said a state security officer at the hospital sharply disputed Carromero’s story and appeared to intimidate him into changing it.

Why would the government of Raúl Castro seek to kill a dissident whom it had left unmolested for a decade? After all, the regime has been seeking accommodation with the Catholic Church and Western governments; it has released most political prisoners (including Iglesias) and introduced modest economic reforms. Iglesias thinks he knows the answer to that. Payá, he says, had become an obstacle to Castro’s strategy, labeling the liberalization “the fraudulent change” and organizing support for an alternative platform demanding free elections.

The July 22 accident was the second one involving Payá in less than two months. On June 2, a Volkswagen van Payá was driving in Havana was struck by a taxi that Iglesias says was driven by a retired police officer.

Is all this coincidence and conspiracy theory? Could be. But a couple of things are striking about the case Iglesias lays out. First, it’s hardly implausible that the Cuban regime would pursue a leading dissident on a road trip; cause his death by accident or intention; and then try to blackmail the survivors into silence.

Also, as long as the Castros continue to rule Cuba, it probably won’t be possible to determine the truth.