Use the Goblin Transport Vessel just northeast of the celebration grounds at
/way #71 68.0 41.0 Pre-Calibrated Goblin Transport Vessel
In Borean Tundra, find Rexxar at
/way #114 77.30 46.16 Rexxar
Use your Torch of Pyrreth and Idol of Ohn'ahra at these spots:
/way #114 85.9 34 (Note 1 & 2 inside and outside the hut)
/way #114 88.0 34.6 (Note 3 in the bushes)
Then head to Sholazar and click the telescope at
/way #119 49.7 36.0 (On top of Pillar)
Fly up towards Icecrown to
/way #118 16 58.8 Scrapes Corpse
Use the Spirit's Whistle to summon Rexxar and tell him that Scrapes was killed by a shapeshifter. Return to Caverns of Time to turn in.