"Well, it happened accidentally, when I went to find the herbalist from that night…"
Previously, when Kel had spent time replaying the events of the night of Lucy's poisoning in her mind, she'd come across one particular occurrence that didn't make sense.
That night, the doctor had been the first to come rushing in the room to attend to Lucy. He inspected the patient and quickly got to work alleviating her symptoms as best he could.
Next came the herbalist, who also immediately ran to inspect the patient.
She checked a few things on Lucy's body, diagnosed the poison, and handed over the antidote.
It would have been a perfectly logical order of events..
If the very knife Lucy had been slashed with wasn't left in the room.
No matter how confident an herbalist was in their knowledge and skills, when it comes to identifying poison, checking the source is always more efficient than checking the afflicted.