The person Wei Ling was calling was the policeman Zheng Tan had met last time. He was Wei Ling's senior in martial arts.
Zheng Tan had heard Wei Ling address him as 'Walnut' in past calls, but did not know the guy's real name. From the sound of things, this 'Walnut' would be moving up the ranks if he cracked this case.
Apparently, he was in line for a promotion already last month, but Walnut was stubborn. He refused to accept the promotion, like he said earlier, if he couldn't solve this case.
Zheng Tan's opinion of the man was that he probably got kicked in the head by a donkey. He had made all the right friends, and the promotion was bound to happen. Yet, he had to be stubborn.
Wei Ling called Brother Walnut several times, but his phone was turned off. Wei Ling frowned; he was becoming worried. He thought about it for a moment, then dialed another number, this time to someone else.