In 1956, Louis Carré bought, on the advice of his friend Jean Monnet, a piece of land near Paris in order to build a new house. Wil Grohmann, a Berlin art critic, put him in touch with the Finnish architect Alvar Aalto, who would complete the construction of this house three years later. This historical anecdote is the origin of a trip through Europe that links the Carré house and the experimental house, built in Finland by Aalto, with buildings located in Brussels, Venice and Porto. These places, whose history resonates with European history, question, thanks to knowledge from the sciences, the existence of the membranes (whatever it is : a micro-organism, a house, a state, …) that allow a place to develop, to interact with the outside world. In the end, this film favors the notion of exchange over that of borders and evokes the possibility of tracing other paths within the European space.