Plant 42 is located in the Guardhouse's main research lab. There are two ways to defeat Plant 42:

- Method 1 (Recommended): The V-JOLT Solution: In the Guardhouse, you'll find a room with a chemical mixer. You need to combine specific chemicals (Water, UMB No. 2, and UMB No. 4) to create the V-JOLT. Once you have the V-JOLT, take it to the room directly above Plant 42's roots (often a bathroom or small storage room). Pour the V-JOLT into the roots. This will severely weaken Plant 42, making the boss fight much easier.
- Method 2: Direct Combat: If you don't use the V-JOLT, Plant 42 will be much tougher. It attacks with its tentacles and poisonous spores. Aim for the central bulb. Shotgun and Grenade Launcher are highly effective.
After weakening it with V-JOLT, enter the room with Plant 42. It will still attack, but its health will be significantly reduced. A few shotgun blasts or handgun clips should be enough to finish it off. If playing as Jill, Barry may assist you in this fight, making it even easier. Defeating Plant 42 grants you access to new areas within the Guardhouse and a key item for further progression.