From Tiny Acorns/Quick guide

Walkthrough

 * Talk to Darren.
 * Go varrock quare talk to urist loric (by craft stall)
 * Talk to market guard go through all chat options
 * Pickpocket urist
 * Walk north of urist and left click talisman
 * Speak to urist
 * Run to guard quickly, right click guard while uric picks up talisman and distract.
 * Steal from stall
 * Talk to uric for bankers not
 * Go backto lumby and talk to Darren

Reward
thieving guild expansion