datamap problem

I am running Twine 2.0.11 of Linux Mint and I have a problem.

I am following a video tutorial, by Dan Cox and I get an error message "You can't get data values from the number 0" when retrieving info from the datamap.

The variables are $weapons, $rooms and $suspects and is coded as such:

{
(set: $weapons to (datamap: "Candlestick", true, "Knife", false, "Leadpipe", false, "Revolver", false, "Rope", false, "Wrench", false))

(set: $rooms to (datamap: "Ballroom", true, "Kitchen", false, "Conservatory", false, "Dining Room", false, "Cellar", false, "Hall", false, "Lounge", false, "Study", false))

(set: $suspects to (datamap: "MissScarlett", true, "ProfessorPlum", false, "MrsPeacock", false, "MrGreen", false, "ColonelMustard", false, "MrsWhite", false))
}

This is the first time I have tried something this complicated. Can someone tell me if the problem is either me or Twine?

Many thanks

J