If ANY of this ties into that "other" series I will turn on Picard in a heart beat. Control was an ill-conceived and poorly-executed idea to begin with.
Also love how Icheb, Hugh and Brian Brophy are now retroactively finding their way on to fans' all time favorite character lists. That painfully dull Icheb got off light. As for Brophy and Hugh they had what, three episodes between them? FFS.
They've set the bar rather high so far as what the secret is that will drive you mad. Think about it - what truth could tear your mind apart? Perhaps a truth that shatters your very notion of existence. Perhaps, the knowledge that you weren't real? I wondered if this is what happened thousands of years ago. A race of synths were created that were near-sentience. At some point, they developed full sentience, but went insane when they became aware of their own existence. If anyone's seen David Tennant's Doctor Who - remember he said the Cybermen had inhibitors as they would go mad without them. Something along those lines. Synths went on a planet-destroying rampage... (?)
Probably not. There's the issue with the Romulan ship assimilated and whether the secret ties in with The Borg. Why was Soji on The Cube - was it to dig deeper into The Borg, or The Romulans? Perhaps the latter.