Zachary did not bury himself in work right after returning to his office. Instead, he gave his mother a call.
Since he was not the type to contact his mother unless necessary, Tania was on tenterhooks when she got the call from her eldest son.
The way she saw it, her eldest son would only call her for huge matters. Hence, she was nervous and afraid, especially now that Zachary and Serenity had not gotten back together. As a mother and mother-in-law, Tania felt helpless about the situation.