Please provide explanation with your answers. Simply posting code does not spread knowledge of integral scripting processes which helps people understand the logic and reasoning behind your answer.
You're putting "Player" instead of "plr", where you defined it.
Your code would instead be
1 | script.Parent.ClickDetector.MouseClick:Connect( function (Player) |
2 | local PlayerGui = Player:WaitForChild( "PlayerGui" ) |
3 | local Suspect = game.Players:FindFirstChild(Player.Backpack.Grab.Suspect.Value) |
5 | local Gui = game.ServerStorage.NYPDBookPlayer:Clone() |
7 | Gui.Suspect.Value = Suspect |