Read the passage and try to guess the object of smuggling

Sam Lewis was a customs officer. He used to work in a small border town. It wasn't a busy town and there wasn't much work. The road was usually very quiet and there weren't many travellers. It wasn't a very interesting job, but Sam liked an easy life. About once a week, he used to meet an old man. His name was Draper. He always used to arrive at the border early in the morning in a big truck. The truck was always empty. After a while Sam became suspicious. He often used to search the truck, but he never found anything. One day he asked Draper about his job. Draper laughed and said, “I’m a smuggler”.

Last year Sam retired. He spent his savings on an expensive holiday. He flew to Bermuda, and stayed in a luxury hotel. One day, he was sitting by the pool and opposite him he saw Draper drinking champagne. Sam walked over.

Sam Hello, there!

Draper Hi!

Sam Do you remember me?

Draper Yes... of course I do. You're a customs officer.

Sam I used to be, but I'm not any more. I retired last month. I often used to search your truck…

Draper...but you never found anything!

Sam No, I didn't. Can I ask you something?

Draper Of course you can.

Sam Were you a smuggler?

Draper Of course I was.

Sam But... the truck was always empty. What were you smuggling?