[S5E21] The Squab And The Quail
Esposito says that there was a kitchen door propped open and there is a uniform that was tossed in the garbage, anyone could have poisoned the food. One of the wait staff noticed a short man with dark hair in the back of the kitchen. Esposito found information that the victim closed one of his plants and 200 people were put out of work, he then got death threats. The poison was some sort of paralyzing agent, it was chemically synthesized. It appears that the victim did not order the quail, it was supposed to go to Eric, Arthur was killed by accident.
[S5E21] The Squab and the Quail