He knows better than to think Callaghan will use that number unless he absolutely has to, but it does make him feel better. If that emergency ever does come, at least Robert will have someone to reach out to.

Tadashi glances down at the hat still in his hand, the bend on the brim rather more extreme than it was at the start of their conversation, and then fixes Callaghan with an only slightly awkward smile.

"... I should go. Hiro's still at home."

And probably wondering why his big brother's been gone so long.