Back at Special Circumstances, Tally tells Cable that Shay talked about David and the Smoke, the town where he lives in the wilderness.
Tally hands over Shay's coded instructions on how to find the Smoke, but Dr. Cable already has a copy of those instruction. Only, since it's in code, she can't figure it out.
Which is why Cable wants Tally to go find the Smoke on her own. Cable provides Tally with a set of equipment for camping—water purifier, solar-powered hoverboard, dehydrated food, sleeping bag, set of Doctor WhoDVDs. The usual.
And Cable also gives her a tracking device in the form of a heart-shaped pendant on a necklace to activate when she gets to the Smoke.
Tally's still feeling a little hesitant, until Cable reminds her of the blackmail situation: "Either Tally infiltrated the Smoke and betrayed Shay, or she'd be an ugly for life" (64).