PlayerGui is not a valid member of Player?

hev=true
on=false
mouse=game.Players.LocalPlayer:GetMouse()
plr=game.Players.LocalPlayer
char=game.Players.LocalPlayer.Character
--variables--
if hev==true then
    plr.PlayerGui.ScreenGui.Frame.left.Visible=true
    mouse.KeyDown:connect(function(key)
        --do something
    end)
end

error: PlayerGui is not a valid member of Player

Script 'Players.Player1.Backpack.LocalScript', Line 8