What is the main conflict in The Long Dark Tea-time of the Soul by Douglas Adams?

Kate Schechter is trying to make a trip from London to Norway, but she feels like the gods are trying to prevent her. In fact, several Norse gods are continuing an old fight, and Kate finds herself in the middle of it, along with holistic detective Dirk Gently. Dirk tries to crack the case while he and Kate travel to Valhalla and back.