While Staying at Smith Hotel Corp

While staying at Smith Hotel Corp., Nina asked her son to take her two diamond rings to the hotel clerk for safekeeping. The rings were shown to the clerk and then placed in a "safe-deposit envelope" which was sealed. The son received a depositor's check stub, which had a number corresponding to the number on the envelope. The envelope was kept in a safe, located in the hotel's front desk, which was used to keep the hotel's cash as well as the valuables of guests. Though equipped with a combination lock, the safe was usually kept unlocked as there would always be a clerk on duty at the reception desk. The following night, the hotel was robbed by two armed men and Nina's rings were taken. She sued the hotel for the value of the rings. The hotel claimed that the robbery was an "act of a public enemy" that relieved the hotel of liability. If the safe-deposit envelope is analyzed in the way that safety deposit boxes are, was the hotelkeeper liable for the theft of property left with it for safekeeping?