Marsupials and Murder

Fenella Woods has been living on the Isle of Man for a year, and it now seems as if every charity there feels it's appropriate to start soliciting her. Most of the letters get turned over to Fenella's advocate to deal with, but one request catches Fenella's eye.

Darrell Higgins wants her help monitoring the wild wallaby population in the Curraghs wetlands area of the island.
When she agrees to spend an hour in the wetlands one morning, the man in her life, Daniel Robinson, offers to join her. After a boring hour in the cold and rain, they both can't wait to get indoors, but on the walk back to Daniel's car, they find Darrell under a bush, dead.

There isn't any shortage of suspects, from volunteers with the charity to business colleagues of the dead man, not to mention a quartet of ex-wives and one current girlfriend, but motive is harder to determine. Can Daniel and Fenella work out who killed the island's main marsupial supporter before the killer chooses another victim?