Tommy is left confused next week as loan shark Rick Neelan orders him to get his job back at the garage. Later, the reason for this becomes clear as Rick forces Tommy to put drugs behind the door panels of a car which is dropped off at the business.
The storyline development comes as Rick continues to hound Tommy, wanting him to settle the debts of his wayward father Terry.
However, Fountain told Soaplife that Rick later puts pressure on Tommy to carry out more jobs.
The actor explained: "Tommy's horrified. He's never been around anything like this before and he's out of his depth. But he knows Rick means business and he has no choice.
"He doesn't tell [Tina] because he knows how much it would hurt her. It's a big deal, but he's blind to the consequences because he just wants to wipe the debt and get free of Rick.
"Tommy thinks it's just one job, but then he gets more and more jobs from Rick and he realises there's no release. It just keeps getting worse. Tommy ends up in really deep trouble."
Tommy starts working for Rick in episodes airing next week.