u/hgw22-7

In 6x12, Jack tells the Russian consulate security chief to help by calling 310-597-3781 (CTU), ask for Bill Buchanan and tell them of Gredenko's location in Shadow Valley.

Then, in 6x17, Cheng calls Jack, informs him that Audrey is alive and that if he wants to see her again, he has to call Cheng back in ten minutes on.... guess what, 310-597-3781.

Believe me, I absolutely love 24. I have to absolutely re-watch the whole show once a year. I have been doing it since 24 first came out. I didn't notice this till now. 😎