Jack heard her call out and yelled back, "Alright!" as he walked out of the greenhouse and along the catwalks high overhead. He was worried about her... her an Ianto both. He'd barely seen much of the young man lately, and he knew Gwen wasn't holding up as well as she was pretending to.
But instead of pushing or trying to mother them, he just kept his office door open in case either wanted to talk.