Geraldine McAllister is desperate for news of 19-year-old Jamie McAllister, who disappeared four days ago.
He was last seen on Monday and his absence has left his family sick with worry.
Mrs McAllister, 61, begged her grandson to get in touch. She said: "Please just get in touch, Jamie. If there is anything worrying you, it's not a problem. I just need you to get in touch, a phone call, a text message, anything."
Jamie, who is originally from Knightswood in Glasgow, was last seen at his flat in Rowan Road, in Cumbernauld on Monday afternoon.
He sent a text to his friend at around 3am the same day, and that was the last time his mobile phone was used.
Mrs McAllister, a pub manager from Airdrie, added: "We are going through hell, it's a nightmare. I'm just numb and I can't even bring myself to think about where Jamie might be. We have tried everything and looked everywhere, it just feels like we're grasping at straws now.
"We don't know what the text said, but his friend said Jamie sounded vulnerable. We're a really close family and he has never said anything was wrong.You read about this happening to other families, but you never think it's going to happen to you."