Mockingbird, Issue #4 takes place initially in Kazakhstan, where hundreds of thousands of Saiga antelopes have died off due to a mysterious bacteria. Agent 19 finds out that it's the same pathogen that's in her system, only she isn't dead. A week later, she is in a tropical paradise, saving her ex-husband, the esteemed Clint Barton. He's about to be vivisected by a group of terrorists in aquatic suits.
Issue #4 has the same twisted humor of Issues #1 through #3. The creators are more interested in developing Mockingbird's character than developing the story of her medical treatment, which is fine, reminiscent of The X-Files, giving off little clues as to the actual story here and there before the big finale, which is scheduled to be Issue #5, I'm guessing. At the end of this issue, she talks about having a doctor's appointment.