Zsolt Battis receives documents from Annika Thanatos for safekeeping, after receiving death threats visiting London. Her friend Symi Heyman informs Zsolt of Annika's death. Zsolt grieves for her and intrigued by Symi's repeated requests for Annika's letters, he'll use them to revenge her death.
As portrait artist he gains the trust of Symi and her confidant.
Symi introduces him to Marcel Lasri at Tate Modern. Tango Man will constantly challenge Zsolt about Symi, persuading her and Helen Bydand, her soulmate to join his Tango Argentino school.
At a party in Helen's Hampstead home, an angry Zsolt saves Symi from an abusive Marcel, he chases to the Heath Ponds, where Marcel disappears between the bathers. He waylays Zsolt, knifing him.
Under Helen's and Symi's care Zsolt recovers. He meets Susan Bolag, who seduces him while he paints her.
Zsolt meets Susan by accident in Budapest and she reveals to him part of her secret life. On Helen's call to Zsolt that Marcel's men have abducted Symi, Susan shares with him secrets about the ring of Informers, she is part of.
Helen and Zsolt race to Paris, realizing that they are followed.
Marcel foils the handover of Symi for bribe-money to their guards and rescuing Symi, he is hit unconscious by Marcel.
Helen, rushing to save Symi, perishes on an exploding bus. John, Zsolt's cousin has decoded the message in Annika's letters. Tate Modern is celebrating, bombs are primed, as Zsolt has to save Symi from the Tango Man's deadly dance.