Background: The COVID-19 pandemic and the measures to protect the physically vulnerable may disproportionately affect people with mental health vulnerabilities, who receive psychotherapeutic inpatient treatment, as many of these measures impact the (inter)subjective space crucial to psychotherapy. Objective: We investigate how people with pre-existing mental health conditions and healthcare professionals experienced changes linked to the COVID-19 pandemic. Methods: During the first COVID-19 outbreak and lockdown in spring 2020, we conducted semi-structured interviews with patients and healthcare professionals at a clinic for psychosomatic medicine in Germany and analyzed them following the principles of descriptive phenomenology focusing on social interactions, intersubjectivity, and the therapeutic space. Results: We conducted a total of >30 h of interviews with 19 patients and 17 healthcare professionals. Analyses revealed that the COVID-19 pandemic and the related measures have led to a sudden loss of a sense of normality. Participants experienced changes in the perception of time, space, self, and embodied interaction with others, resulting in a profound feeling of alienation and “unhomeliness” which seemed to magnify pre-existing psychopathology. The inpatient psychotherapeutic environment provided safety by offering spatial and temporal structures and opportunities for social interaction, supporting people to find new ways to be in a changed world. Conclusions: Our study shows that despite the threat of infection, it is vital to continue to provide people with psychological vulnerabilities with a safe therapeutic space in which to regain a sense of safety in a changed world. This is particularly important, as those people seem to suffer intensely from the collateral measures of a pandemic.