‘On the String’ is the sixth and penultimate instalment in the Magic Crystals series. It picks up immediately after the conclusion of ‘The Cloak of Steel’, at a time when many believe the war is over, although John and some of his friends have misgivings. They are quickly justified when a former ally steals all the usable magic in the world and takes almost everyone prisoner, with only John and a few lucky friends managing to escape his net. It is up to them to be the entire resistance now, all the while knowing that they are on a magical string which could be yanked at any time.

Work began on MC6 in late 2012 and concluded in early 2016. Stephen Hayes had to overcome a number of writer's blocks throughout due to personal circumstances, as well as the additional stress of finally being a published author and having to spend a lot more time on activities he didn't particularly enjoy, such as marketing. It was edited in early 2017 but is not expected to be published until 2018 or 2019.