Nursing critically ill patients includes planning and performing safe discharges from Intensive Care Units (ICU) to the general wards. The aim of this study was to obtain a deeper understanding of the main concern in the ICU transitional process-the care before, during, and after the transfer of ICU patients. Interviews were conducted with 35 Swedish nurses and analysed according to grounded theory. The main concern was the nurses' "struggling with a gap." The "gap" was caused by differences in the altered level of care and contributed to difficulties for nurses encountering an overlap during the transitional care. The categories: Sheltering, seeking organizational intertwining and striving for control are related to the core category and were used to generate a theory. The nurses sought improved collaboration, and employed patient-centred routines. They wanted access to necessary tools; they relayed or questioned their own competence and sought assurance of the patients' ability to be transferred. If the nurses felt a loss of control, lack of intertwining and lack of collaboration, they sheltered their patients and themselves. Intertwining was more difficult to perform, but actually even more important to do. With knowledge about ICU transitional care, collaboration, routines, and with an organization that provides an educational environment, the process could be improved.