Mr. Smith is telling two funny stories of his police work. Story A I remember catching a "thief" in a clothes shop once. It was strange. The man was hiding a yellow sweater inside his coat. I thought he had stolen it, so I caught him. We found later that his wife gave him the sweater for his birthday, but he hated it. He just wanted to return it to the shop for money, but he didn't want his wife to see him! We soon let him go. Story B Another day, a man called Bob went into a bank on Sixth Street. He wrote on the back of an envelope, "Give me the money! Or I'll kill you." and gave it to the bank clerk. She gave him $100,000 and the man ran away. Then we received a phone call from the bank clerk. She told us to go to the man's house in Candy Town and get him. We caught him as soon as he got out of the elevator. He couldn't believe that we found him so quickly. We told him that the front of the envelope he used his name and address on it! Mr. Smith caught the man in the clothes shop   _  .
by exchange by mistake by accident with the help of others'