Batman/Green Arrow: The Poison Tomorrow 1992 NM-

Batman/Green Arrow: The Poison Tomorrow, released by DC Comics in October 1992, is a 64-page prestige-format one-shot graphic novel.

Written by the legendary Denny O'Neil and illustrated by Michael Netzer, this comic forces the Dark Knight and the Emerald Archer into an uneasy, high-stakes alliance to prevent a global ecological disaster. 

This response includes a look at the original graphic novel release:

Core Plot Summary

• Black Canary is Poisoned: The story kicks off when Dinah Lance (Black Canary) falls deathly ill. She has been infected with a fast-acting, lethal biological serum.
• The Hunt Begins: A desperate and headstrong Oliver Queen (Green Arrow) tracks the origin of the bio-toxin to Gotham City. His reckless, tunnel-vision crusade to find a cure immediately puts him at odds with Batman, who is tracking the broader biological threat. 
• Poison Ivy's Extinction Plot: The trail leads both heroes directly to Pamela Isley (Poison Ivy). Ivy has concocted a devastating, world-threatening plague. Driven by an extreme eco-terrorist ideology, she intends to wipe out a significant portion of the human population to reset the planet's ecosystem, crowning herself the "mother of the men of tomorrow".
• Clashing Philosophies: The narrative centers heavily on the ideological conflict between the two heroes. Green Arrow is entirely focused on saving his girlfriend, willing to break any rule to get the antidote. Batman, meanwhile, focuses on the bigger picture—stopping Ivy's mass-extinction weapon before it can be unleashed across the globe.