How to concatenate a string?

So in this function I have (which I have previously asked a question about) I find the player who hit a brick and then find their bus in the workspace. However I recieve an error trying to concatenate this string.

Detector = script.Parent

function onTouch(part)
	local player = game.Players:GetPlayerFromCharacter(part)
	local bus = Workspace:FindFirstChild(player.."'s Car")
-- do stuff
end
Detector.Touched:connect(onTouch)

The model in the workspace is called "Player 1's Car" (in test mode) but the function breaks when I do this. Can anyone see why?