Script gives error when I plug in a variable into the function? [unanswered]

So this is my lightning script for my game and for some reason it stopped working at the zap function when I try to do bolt()

function bolt(pos)
            local CF = CFrame.new(workspace.Cloud.Position, pos) -- error
            local sound = script.StrikeSound:clone()
            sound.Volume = 1
            sound.Name = "Temp"..sound.Name
            sound.Parent = script
            game.Debris:AddItem(sound,10)
            for strike = 1, 8 do
            local lastPos = CF.p
                local Parts = 7
                local Arc = 20
                game.Lighting.Ambient = script.Flash.Value
                for i = 1, Parts do
                    local targpoint = CF.p + ((CF.lookVector*((CF.p-pos).magnitude/Parts))*i) + Vector3.new(math.random(-Arc,Arc),math.random(-Arc,Arc),math.random(-Arc,Arc)) -- eror
                    if i == Parts then
                        targpoint = pos
                    end
                    local s = Instance.new("Part")
                    s.formFactor = 0
                    s.Size = Vector3.new(1,1,math.floor((lastPos-targpoint).magnitude))
                    s.CFrame = CFrame.new((lastPos+targpoint)/2,targpoint)
                    s.BrickColor = BrickColor.new("Bright yellow")
                    s.Anchored = true
                    s.CanCollide = false
                    local m = Instance.new("BlockMesh")
                    m.Scale = Vector3.new(5,5,1)
                    m.Parent = s
                    local sc = script.BoltScript:clone()
                    print'incoming lightning'
                    sc.Disabled = false
                    sc.Parent = s
                    s.Parent = workspace
                    lastPos = targpoint

                end
                wait(0.07)
                game.Lighting.Ambient = script.Storm.Value
                wait(0.01)
            end
        end