Placing a part between 2 Vector3 values

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1

I’ve been working on a script in which creates a part and the original idea is to have it just go to the front side of the player, but later decided to revamp it to make it go between the players HRP and the mouse positioning, without changing the size of the beam.

What happens: https://gyazo.com/a774111e30cbcfbfa2a1d3f624a45ebd

Local script (firing event):

uis.InputBegan:Connect(function(input,GPE)
	if not GPE and input.KeyCode == Enum.KeyCode.F then
		local mouse = plr:GetMouse()
		game.ReplicatedStorage.Kamehameha:FireServer(mouse.Hit.p)
		local t = Instance.new("Animation")
		t.AnimationId = "rbxassetid://7409187320"

		local td = Animator:LoadAnimation(t)
		td.Priority = Enum.AnimationPriority.Action
		td.Looped = false
		td:Play()
	end
end)

Server Script (important part):

new.Beam.CFrame = CFrame.new(plr.Character.HumanoidRootPart.Position,mouse)*CFrame.Angles(1.5708,0,0)
new.Beam.CFrame = new.Beam.CFrame*CFrame.new(0,0,-43)