At least when it comes to Orthodoxy, perhaps one can doubt what Fr. Martin says.
Wikipedia's entry on him reports:
Martin said concerning the three secrets of the Virgin Mary as Queen of Heaven in Fátima in 1917, she mandated the pope of 1960 to consecrate Russia to her Immaculate Heart. The Russian orthodox church would then convert back. If the mandate were not followed, devastating war in the world and destruction inside the church (The Great Apostasy) would follow.
The three secrets were given in July 1917 when Russia's government was not yet Bolshevik, ie. it was not yet a secular government that discouraged the Church. Therefore, when it mentions "convert back", it suggests it has in mind an idea that Orthodoxy left Catholicism and return to it. However, perhaps it meant reconvert to Christianity, but I am not sure.
Second, the entry says:
Pope John Paul I was murdered according to Malachi's book, Vatican: A Novel, by Jean-Marie Villot, formerly Cardinal Secretary of State under Pope Paul VI, under orders from the U.S.S.R..
This however is a strange claim. The day before Pople J.P. I's death I believe the Pope met and ate or drank with the Russian Church representative, who himself strangely died soon after that meeting. In other words, I think it was not really the Russians who were killing them.
On page 287-289 of his book "Keys of This Blood: Pope John Paul II Versus Russia", Fr. Martin appears to take a negative, patronizing tone towards Orthodoxy. He basically portrays it as phyletist ("geopolitical") and stuck in its traditions (that's ironic- Fr. Martin should know the importance of tradition), and delusional about lost grandeur. He then portrays Byzantium's and Russia's ideas about the 2nd and 3rd Rome as delusional.
I was expecting something more tolerant from Fr. Martin, unfortunately, since he also criticizes Russian Orthodoxy for being anti-papal and threatened by expansion of Papal power. In other words, he criticizes Orthodox for not being tolerant enough.