Twenty years after the Holocaust, Germany and Israel signed contracts for scientific collaborations. Fifty years later, those collaborations have become an asset for science in both countries. Notwithstanding those win-win collaborations, the trauma of the Holocaust still casts a long shadow over them, creating uncanny experiences and fear. This paper reports findings from interviews with 125 Israeli scientists who have collaborated with German colleagues. It employs Freud’s analysis of the uncanny, an experience which mixes cozy familiarity with a sense of eeriness, confronting subjects with unconscious, repressed personal impulses or memories. The paper extends Freud’s analyses by showing that uncanny experiences may result from a cultural – rather than a personal – trauma. Specifically, the results show that while Israeli scientists enjoy their collaborations with German colleagues, they occasionally experience fear and unease in their presence. Some identify Nazi mnemonics, others report on uncanny moments in their partners’ homes. Those uncanny experiences appear among young and old scientists alike, suggesting that their scientific reason is captive of the cultural trauma of the Holocaust. I conclude by pointing that Israeli scientists are captives of their national trauma just as ordinary people are. Their reason proves to be a weak counterforce in mitigating the eruption of repressed emotions generated by the cultural trauma of the Holocaust.