As previously revealed, a future plot will see Gaz sell a supply of the dangerous drugs to Carl's son Seth (Miles Higson), who is looking for a quick way to improve his physique.
However, the pair's actions lead to a shock hospital dash as Seth ends up collapsing during an intense workout session when the strain becomes too much.
Soon afterwards, Seth's mother Heidi discovers Gaz's role in the incident - leaving the rogue wondering whether she will share the news with her husband.
Speaking to Inside Soap, Goonan commented: "Heidi's understandably livid. She does come round to the idea that it isn't totally his fault, but she certainly isn't able to forgive him for it."
Reflecting on Carl's short-tempered ways, he continued: "Gaz knows that Carl can be a bit of a live-wire. Despite his bravado, Gaz is really scared of what Carl will do if he finds out - but he'll try to hide that fear as much as he can until it actually happens."
Seth's collapse airs next Monday at 6.30pm on Channel 4.
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