Regarding sending San Tuo to carry out the assassination, a significant reason was to probe, and this, Gongsun Mo admitted.
However, he did not expect that San Tuo would fail to bring back any useful intelligence.
If it weren't for the fact that he thought he understood Li Fei's character, Gongsun Mo would have really suspected whether San Tuo had already defected to Li Fei.
Now Gongsun Mo was growing quite weary of San Tuo, seeing him as a disease that was too prideful to recognize a favor. San Tuo once harbored such naive hopes, but after this incident, even a fool should smell something amiss and realize the last time was just exploitation, and he never intended to give San Tuo the thousand-year ice silkworm.