Shen Mo employed The Big Dipper Array to trap the Ghost Bride while simultaneously conversing with Chen Mengze using a Sound Transmission Talisman.
He warned her that after breaking the Prohibition, she must immediately leave the Ghost Bride's haunted courtyard and not wade into troubled waters with other cultivators.
He did not intend for Chen Mengze to join him immediately.
Once the Prohibition on the ghost house was broken, the red sedan would also be destroyed.
At that point, he planned to use the Soul Refining Flag to attempt to refine the Ghost Bride.
The Soul Refining Flag was, fundamentally, an evil cultivator's tool; for others to see it would be far from ideal.
Not to mention, the Soul Refining Flag held captive nearly a hundred Heavenly Demon Soul Generals.
With a sect prohibition in place, it would be even harder to explain this to Chen Mengze; it was better to find her afterward.
BANG!
BANG! BANG!