Snape had arrived at the gates a few minutes early, taking the opportunity to review the defensive charms on the gates and walls in person.
When Theo arrived, Snape opened the gates for him; in response to his thanks he murmured "Not at all." He offered Theo his hand, Side-Alonging them to his office without further ado.
"What did he have to say?" Snape asked at once. No need to say who he was.
"What can I do to help?" There must be something, Snape knew, or Theo wouldn't be here.