VENICE, Italy, Sept 1 (Reuters) - Spanish director Pedro Almodovar shines a spotlight on the tens of thousands of people who disappeared during the civil war and Franco"s dictatorship in his latest film "Parallel Mothers", which opens the Venice film festival on Wednesday. The film, starring Penelope Cruz as one of two women giving birth in the same Madrid hospital on the same day, is a reflection on motherhood and the importance of family ties. But it also dwells on a painful chapter of Spanish history that the country is still struggling to come to terms with. Almost 50 years after the death of General Francisco Franco, more than 100,000 victims of summary executions during the 1936-39 civil war and the authoritarian rule that followed remain buried in unmarked mass graves dotted all over Spain. The majority were Republicans or leftist sympathisers killed by fascist forces, and their relatives seeking a dignified closure have often received little help from Spanish authorities to locate and excavate their remains. "I wanted to give this topic visibility, and I believe that in Spain after 85 years, until we"ve paid this debt we owe to the "desaparecidos", we will not be able to close the chapter of our recent history," Almodovar told reporters. He said Spain was still reluctant to confront its troubled and divisive past, despite some steps taken by the government in recent years to fund the locating of mass graves and the identification of the dead. "We can"t just close our eyes in front of what happened," the 71-year old Oscar-winning film-maker said after a press screening ahead of the official presentation on Wednesday. In the film, Cruz plays Janis, a single woman near her forties who unexpectedly falls pregnant - just like teenager Ana, whom Janis meets in hospital on the day they are each due to give birth to a baby girl. Their lives become increasingly intertwined when the man Janis had an affair with asks for a paternity test, while she also looks for help to exhume the body of her great-grandfather, murdered by Franco"s forces. Cruz, an Almodovar favourite who says she decided to become an actress after seeing one of his films at 16, said Janis was her most complex character so far and she felt very privileged to work once again with the film-maker who helped make her a celebrity. "I feel like the luckiest girl in the world, being able to work with him for so many years, seven different projects and so many different characters. "I respect him too much to bombard him with requests but I know that when he thinks a film is right for me, he"ll call."