The following article contains spoilers for Future State: Gotham #13, on sale now from DC Comics.
Nightwing (aka Dick Grayson) has always been the best and brightest of the Bat-Family, the proverbial light to Batman's darkness. However, in Future State: Gotham #13 (by Dennis Culver, Geoffo, and Troy Peteri), Nightwing's behavior has become increasingly concerning. After his recent overdose of the drug brane, he has started using a delivery system in his new Bat-suit to automatically dose himself. The drug gives him enhanced abilities, but it may also be hindering his ability to feel emotions.
Brane has given Nightwing insight into the past, present, and future. He's seen visions of a calamity coming for the world, as well as learned where long-lost family members have been, in addition to discovering that allies he thought dead were alive. Despite all this, he hasn't once shown any emotional reaction to any of it beyond a dogged determination to avert whatever catastrophe is on the horizon.
There were obviously risks involved in overdosing on brane. When Talia al Ghul and Nightwing concocted a plan to discover Damian Wayne's fate they knew there was a good chance Nightwing could die. Thankfully, he survived, but it seems neither of them were prepared for the aftereffects. The ability to psychically perceive what he could not be aware of himself was always a benefit of brane, but it seems to come at the cost of Grayson's emotional response.
In the span of a few hours, Nightwing became aware that not only had Damian been suffering alone in hell all this time, but that Bruce Wayne, the man he considers his father, was actually alive. At least one of these revelations should have evoked feelings from Grayson, but he didn't even blink.
Instead, he merely informed Talia how to find her son, without going into much detail about what became of him. He then immediately set about becoming the latest Batman, embarking on some unknown quest to save the world. The notion of having to become Batman again to protect the world should have caused some kind of reaction from him, considering that he has never been happy about operating in the role.
Yet, despite all these significant changes in his life, Nightwing has taken it all in without missing a beat. This suggests that an unforeseen consequence of the overdose is that it limited Grayson's ability to feel emotions in a healthy way. This certainly tracks with the nature of the drug, prioritizing the mind over the heart in a metaphorical sense.
Despite all the benefits brane has given him, it may have cost Nightwing in the long run. While his plan seems to end with his family reunited, he appears to not even have the capacity to experience joy even if his mission is successful. In trying to fix the problems in his life, Grayson might have permanently damaged his ability to feel love.
There is one other possibility that is just as troubling. It's possible that Nightwing has no choice but to be emotionless. Whatever he saw coming in the future was bad enough to force him to reclaim the cape and cowl. Perhaps it was so terrifying he had to numb himself just to be able to function. That however, could cost everyone considering how important Grayson's heart and feelings are to his successful operation as a hero.