KGB agent, spy, traitor or mafia, who is who?

In this second book of the series, Artur the KGB agent who has infiltrated in the Jewish family of Sofia and Mendell is starting to get desperate. He knows Sofia is involved in the exchange of information to the Americans, stories about how Jews are treated in Russia and in the Gulag, but Artur doesn't know exactly how and who is involved. The reason the KGB wants this information is that the stories are stalling negotiations about nuclear disarmament because there is pressure from human rights organisations.
Artur, in the family of Sofia known as Yoseph, is supposed to seduce Sofia but she is still loyal to Mendell, the man she used to love but who came back as a different man from the Gulag.
Other family members like Sofia's sister Vera, Sofia's son Kolya and her parents are also under investigation. Who does what and what is it exactly they do.
When both the CIA and the Russian mafia are involved, things become very complicated and unclear what is everyones role.
It's difficult for Artur to seduce Sofia while his real feelings for her are in the way. He has to choose between his mission and his love for her. While he is hunting a spy, he doesn't know for sure who the spy is. Is it perhaps Sofia or is she just a little part of a bigger organisation.

The characters of Artur is evolving a lot in this book. He doubts a lot about his own duty, can he do what is asked of him and is he prepared to go to any lenght. The love game of attracting and repelling seems to take ages, althought it's just days in the book. He has to jump through many hoops to keep up his cover.
Sofia on the other hand has a lot to deal with her husband. So much that she misses out a lot of what is happening with her younger sister Vera. She has evolved a lot in this book. In the first book she didn't play a big part in the story, but know it's important that she is there because some things she does have a big influence on the events.

You cannot read this book without having read the first one and in the right order. Can't wait for the next part.