Leaving it to Astrid proved to be a correct decision.
With Jack giving her direction, she was able to arrange everything perfectly. Qin Weiqi, now with a different face, left for a journey toward the capital, leaving a will in the hands of the Mercenary Union. Inside was the City Lord's testament and request for protection from the Mercenary Union.
The letter also stated that his will should only be delivered by the Union in person to the recipient.
Qin Shangyu didn't live in the same manor as Qin Weiqi. He was a busy man who worked outside and only visited his adoptive father every now and then, so it wouldn't be strange for him to receive the will through a 3rd party.
With this, they could cover up Qin Weiqi's escape perfectly. The letter and the will would serve as the evidence and proof that the previous City Lord was killed by a third party and his death would not bring shame or doubt upon the Mercenary Union.