By the time that Hudlická returned to Czechoslovakia, just before Christmas, the period of liberalization was over and the USSR had brought in tanks to suppress the Czechoslovak government. In spite of the return to authoritarianism, Hudlická was allowed to present a paper at Oxford's Physiological Society in the summer of 1969. While they were in England, she and her husband made plans to evacuate their family from Czechoslovakia. Soon after their return to the country, on the pretense of a holiday visit with friends, they flew their son to London and sent their daughter to Colmar in northern France. With the children securely out of the country, Hudlická and Klein packed a small suitcase and drove to visit friends in Hungary. From Hungary, the couple drove on to France to meet their daughter, via Austria and Italy. In Paris, they were reunited with their son and the family made their way to Zürich, Switzerland, where they met Hudlická's mother and put her on a plane to USA for a visit with Hudlická's older brother while the family decided where to settle. Their escape occurred just before the Czechoslovakian borders were closed on 15 September 1969.