The book you need to use in the bookshelf to access the room with the giant plant in the guardhouse.
The plant roots in the flooded section doesn't do anything but there is a key in one of the rooms which you need to access the boss room. You'll trigger the boss fight when you pick up the helmet key.

ok thanks, so I am just an idiot

引用自 Pyro-Chan 「Hell Yeah」：

ok thanks, so I am just an idiot

Nah,you're not an idiot. If you've never played RE1 it;s going to be difficult to know what to do.
I'm a huge RE fan been playing since the original in '96,I like how there's custom maps from 1-3/Outbreak to play for L4D2.

I forgot to mention you can create a formula called V-Jolt which you can use on the roots,there's a puzzle for creating it,but it's not necessary really. Spoiler but you'll fight 2 Tanks in the room.

no don't worry, I've already made the v-jolt poison, which is what I meant by bapping the plant

lol dont feel bad, the good think is you are asking for help and trying to beat the campaign, no blaming me like others do ¬¬ tell me when you finish the maps, I wanna if you enjoyed them :P

Hell yeah dude that was some good ♥♥♥♥, you did a good job on it, I also played the second one both side a and b and they were also great.

i have poisened the plant and killed the tankin the room. but after we dont know what to do. we are stuck on this and the server crashed

Grab the Helmet key from the fireplace then head back to the mansion.

How the f**k do you find the damn helmet key?

引用自 The Loch Ness Bombster：

How the f**k do you find the damn helmet key?

It's in the room where you fight 2 Tanks,at the Guardhouse. You need to get the 003 key to access the room,it's the double doors next to the chemical storage room.

You are an idiot. You are welcome.

I'm sorry but which bookshelf are we talking about? I can't find any bookshelf to put the book in anywhere?

引用自 Kedna：

I'm sorry but which bookshelf are we talking about? I can't find any bookshelf to put the book in anywhere?

The bookshelf to put in the red book is in room 003,it's highlighted.

引用自 LilG：

引用自 The Loch Ness Bombster：

How the f**k do you find the damn helmet key?

It's in the room where you fight 2 Tanks,at the Guardhouse. You need to get the 003 key to access the room,it's the double doors next to the chemical storage room.

There are No Tanks at the Guardhouse.

Are you Talking about the Flooded Basement where you Fight the Sharks that Come out of 1 Giant Tank of Water Wich Dose Nothing?

引用自 Conchur The Wise：

ok thanks, so I am just an idiot

Oh I Figured it out. The 003 Room Key is in the Room to the Right of the Room where you Flip the Lever that Drains the Water from the Flooded Basement and in that Room with the Lever is a Button on the Wall that unlocks the Room where the 003 Key is.


The Shelf you use the Red Book on is in Room 003.