Codename for a Laundry project in the late 1990s which was an attempt to revisit the failed RECOIL test series of a decade before. In fact, HELIOTROPE departed almost entirely from using ANNING BLACK specimens in favor of differently-sourced protean shape-shifting entities. Open-air tests were authorized in 1996, but the initial series was so disappointing that the expanded follow-on tests planned for the next year were scrapped and the project shelved indefinitely.
Most of the materials from HELIOTROPE were shipped to Site BOX-ROOM, but some samples were apparently left in secure storage at the test range at Site HEATHER. A break in containment caused several casualties recently in an incident codenamed XXXXX.