Plot summary
"Mouth" McGarry, the manager of a broken-down baseball team called the Hoboken Zephyrs on its last legs, is introduced to Dr. Stillman, an inventor who built a robot named Casey to play on the team. Casey has the ability to throw super-fast balls, super-slow balls, and extreme curveballs that cannot be hit.
Eventually, after Casey is beaned by a ball and given a physical examination, the National League finds out and rules that Casey must be taken off the team because he is not human. Dr. Stillman then installs an artificial heart for Casey.
However, due to his new heart, Casey now possesses human emotions. He refuses to throw his fast balls anymore, saying that he feels empathy with the batter and does not want to ruin the batter's career by striking him out, and quits baseball to become a social worker. With the team sure to fold soon, Dr. Stillman gives McGarry Casey's blueprints as a souvenir. Glancing at them, McGarry suddenly has an idea, and runs after Dr. Stillman to tell him. Rumors later surface intimating that McGarry has used the blueprints to build a world-champion team of Casey robots on the West Coast.
Credits
Adapted from Wikipedia contributors, The Mighty Casey. Paragraphs and formatting adjusted; illustrations, reference markers, block quotations and non-story material omitted.