AN ENGLISH-SPANISH DICTIONARY (GRANADA UNIVERSITY, SPAIN), 14.4
come back in
(v.) = volver a entrar, volver adentro.
Ex: Those who are 'perfectionists' in such things will want to drive you crazy worrying about 'what if two people go out together' or 'it won't be accurate because some users go out for a smoke and then come right back in' or 'what about kids who run in and out' and so forth.