Sofia, 11, and Daniel, 8, did not speak the language and knew nothing about their new home country

The Russian government plane that landed in Moscow from Ankara on Thursday carried an assortment of spies, assassins and criminals, one half of the biggest prisoner exchange since the cold war.

But among the first to descend the stairs to the tarmac, where president Vladimir Putin was waiting to greet the returnees, were two young children, looking wide-eyed and confused.

Sofia, 11, and Daniel, 8, had been born in Argentina. They later moved with their parents, Maria Mayer and Ludwig Gisch, to Slovenia, where Mayer ran an online art gallery and Gisch started an IT company.

Mayer told friends the family had left their home country of Argentina to avoid street crime. The family spoke Spanish at home; the children went to an international school in Ljubljana, where they studied in English.