True Stalker was a Sphinxian treecat who had bonded with Arvin Erhardt. He was known simply as the Stray to other humans.
After Erhardt was murdered (his aircar was sabotaged, in an effort to make his death appear accidental), True Stalker trekked a huge distance across Sphinx in an attempt to find help to avenge his murdered companion. This was extraordinary since the despair and grief involved in losing a human companion almost always caused a treecat to suicide or starve to death.[1]
Against all odds, True Stalker managed to get across enough to Scott MacDallan. With the help of Walks in the Moonlight Clan, including a memory singer known as Clear Singer, McDallan was convinced to investigate and eventually uncover the sabotage. When McDallan went to the BioNeering facility where Erhardt had worked to further investigate, the woman who had killed Arvin, Dr. Muriel Ubel, attempted to kill him as well. Together, Fisher and True Stalker saved McDallan's life and killed Dr. Ubel, but True Stalker was killed in the fight. (HHA2.1: TS, SK1)