Former army officer Troy, played by Dieter Brummer, will also take son Callum and Sonya's sister Jade hostage.
"From Troy's point of view, he just wants to ingratiate himself back into his son's life and everyone is making that really difficult for him," Brummer told TV Week.
"But it's just not to be, as no-one trusts him for a moment, so he locks Callum inside the house and doesn't want him to go until he's said his bit."
When pregnant Sonya and Jade burst in to protect Callum, viewers will be left to wonder whether they will escape unscathed.
Eve Morey, who portrays Sonya, revealed that there is a "devastating" culmination to the storyline.