Outflow‐Infall Interactions in Early Star Formation and Their Impact on the Mass‐assembling Process in L1228

New high-resolution molecular line and continuum millimeter interferometer observations of the environment within 10 4 AU of the low-mass protostar IRAS 20582+7724, in the L1228 dark cloud, enable a detailed study of the molecular outflow near the protostellar source, the circumstellar envelope, and the outflow-envelope interaction. In 12 CO and 13 CO maps a wide-angle molecular outflow has been imaged to within less than 1000 AU of the 2.7 mm continuum emission associated with IRAS 20582+7724. The morphology and kinematics are consistent with entrainment of the gas by an underlying wind that has both a wide-angle and a collimated component. The HCO + (1-0), HNC (1-0), and CS (2-1) lines are sensitive to infall motions and trace an elongated circumstellar envelope perpendicular to the outflow axis. Together the morphology, kinematics, and energetics of both the outflow and infalling circumstellar envelope suggest that the outflow has excavated wide-angle cavities in the envelope and thereby constrained the infall region to a limited volume outside the outflow lobes. In the IRAS 20582+7724 system, outflow-envelope interactions evidently have an important effect on the mass-assembling process. In addition, our multimolecular line data show that the outflow has affected the chemical composition of the gaseous environment surrounding the protostar, through the shock enhancement of different molecular species.