Murder Adjacent #8: Root Cause

Quirky Sleuths. Big Murders. Very Bad Alibis.
Dr. Iris Kestrel is a forensic botanist who prefers plants to people because plants are less ambitious about lying. At the grand opening of Harrowick Colleges restored conservatory, celebrated donor-scientist Dr. Celian Orr is found dead beside a rare toxic plant display. Iriss greenhouse assistant Moss had publicly accused Orr of stealing research, and toxin is found on Mosss gloves.
It is an elegant explanation. It is also biologically impossible.
The plant everyone blames could not have produced the concentration of toxin that killed Orr at that stage of bloom. Something else was used, and someone rearranged nature afterward to tell a cleaner story. As donors panic, administrators protect reputations, and Detective Rook reluctantly learns more plant vocabulary than he ever wanted, Iris follows roots, residue, compost, and growth patterns toward the truth. People may lie constantly. Fortunately, the fern has an alibi.