It is unknown what kind of plant that Plant 42 used to be before the T-virus outbreak, but after being exposed to the virus it mutated into something unlike any other plant on Earth. It became a huge, bulbous thing that hung from the ceiling of Point 42 (from which its name is derived) with its roots creeping down the walls and extending down through the ground and into the Arklay Laboratory's Aqua Ring, where the roots would be able to absorb large amounts of water. Of course, the T-virus mutation also turned the plant carnivorous and over the course of the contamination event, Umbrella staff fell victim to the plant whilst trying to hide from the other creatures roaming the premises. Plant 42 would use its vines to ensnare prey and puncture their bodies with the vines' barbed tips, draining the victims' blood. The creature could also spew poisonous acids from some of its vines and release deadly spores from its bulb.
When the S.T.A.R.S. investigated the mansion's dormitory, they encountered Plant 42 and found it to be a difficult threat to contend with. Using a small chemistry lab on the premises, the S.T.A.R.S. were able to concoct a sample of V-Jolt, a compound designed specifically for destroying plant-based mutations. After contaminating the plant's roots with the V-Jolt, they were able to combat and destroy the plant which had been considerably weakened by the chemical, disabling many of its vines. When its bulb was destroyed, Plant 42 completely withered and died.