When a patient who had been given a day pass arrived back at Unit late and inebriated. Customary search of belongings was omitted due to patient agitation. When patient was finally let onto Unit he pulled a large knife from his coat and started to threaten staff. As the resident on-call, I had to figure out what to do while awaiting security. Grabbed a spare mattress to block patient’s attacks, gathered all staff behind me and we retreated to safety of the lockable central nurses station while awaiting arrival of security team. Next morning, attending psychiatrist commended me for taking the best action when confronted by an agitated patient with a weapon- RETREAT TO SAFETY!