An assassin embroiled in a plot against Queen Victoria is psychically attacked by a mysterious cult, flooding her mind with memories from a madman and inflaming her to pursue the cult’s destruction.

Ah! I see. The cult isn't trying to make the assassin destroy them. The assassin's reaction is to destroy them as revenge for attacking her. It is an unintended side effect.

But on that... The segment "and inflaming her to pursue the cult's destruction." feels wrong to me somehow. I like the 'inflaming' and the 'destruction' words and it closes the logline with the proper intent, but it sounds off to me.

You say the Assassin is psychically attacked by the cult making her want to pursue the cult's destruction.

Not trying to be snippy, but how do you get to the assassin being a part of the cult that attacked her?