Dr. Muriel Ubel was a Manticoran research biologist.
She worked as a scientist for BioNeering on the planet Sphinx. One of her projects attempted to understand the nature of the mechanism by which picket wood trees dissolved the cellulose in the branches connecting them to diseased trees. Her work produced a substance which resulted in an ecological disaster near the facility when accidentally released.
To prevent knowledge of the problem from getting out, she sabotaged an aircar, killing her research assistant and two pilots, one of whom, Arvin Erhardt, was bonded to a treecat. She intended to escape, leaving Sphinx for Mesa and to sell her development to the highest bidder. When Dr. Scott MacDallan discovered what she was doing, she attempted to murder him, but MacDallen's and Erhardt's treecats intervened; the latter jumped in front of her rifle and was killed, distracting her, shifting her aim just enough to allow MacDallan to shoot her instead, all just before his treecat killed her. (HHA2.1: TS)