My overall rating of "The mentalist"'s Season 4: 4/10.
When it comes to pros of this episode, only the reappearance of the character of Erica Flynn comes to mind (OK, Patrick's final trick is cool if you think about how it's done, but the whole context is stupid and it likely wouldn't have worked in reality). "Every rose has its thorn" was a pretty cool episode, although the central question it posited (whether Jane's denial of his attraction to Erica was clouding his judgement) was a bit lame. I wouldn't say the series exactly needed Erica to return, or that there was anything with her character that was yet to be resolved. She certainly is very charismatic and seductive, so what the hey, but the series has been able to craft perfectly fine new charismatic characters (Lisbon's niece, Summer etc), there's no need to be digging through the attic for cool-but-not-particularly-standout characters from past episodes just yet. The fact that the aforementioned lame idea from "ERHIT" reappears, reformulated by Erica in the exact same words in a different context is... strange, bad writing, but hey, Erica could be saying almost anything and remain absolutely magnetic, bad writing has only so much power.
As for the cons: a huge plurality of the scenes in this episode seem very cringy, lame or illogical. Shout out to the character of Grace Van Pelt, who has been made really annoying this season, for delivering what I believe to be the worst line of Season 4, which makes the title of this review. It's so laughable, I don't know whether it was supposed to be satire of the self-righteous traumatised loose cannon cop archetype they've been shoehorning her in - any more and you'd have to rename her character Bosch! But the next scene has that chemistry between Patrick and Erica, and the latter whole demeanour has got to be worth a point above 1/10. "Oh, yes. That. Would you hate me if I told you I was lying?" Brilliant! That can't possibly have been written by the same person as the prior scene, could it?..