Baby Rocco develops a serious infection before falling into a critical condition while in hospital.
Lisa Gormley has spoken to TV Week about her "devastated" and "petrified" alter ego Bianca's reaction to the shocking news.
"She has a lot of anger towards Heath," Gormley declared. "It happens at a really unfortunate time, because Bianca's doubting Heath's ability to look after Rocco on his own, and is worrying about going back to her job at the school and leaving them on their own.
"She has a lot of guilt and a lot of anger towards him. I think with these kind of things, when there's no explanation [as to how he got sick], people lash out at the closest person - and Heath is the closest person to her."
Revealing the extent of the strain between Bianca and Heath, she added: "He's devastated and it causes him a lot of angst. It gets to a point where she inadvertently blames him and he leaves.
"Bianca and Heath come from such different worlds that there are constant clashes of opinions, but you can't help who you love and hopefully they'll be able to work things out."
Australian viewers will see the storyline next week on Channel Seven, while the episodes will air on Channel 5 in November.