Jonah McCarthy was an agent of Checkmate
. Under the cover of a Harvard educated lawyer, he was hired on as part of Wonder Woman
's staff at her Themysciran embassy. He played the part of a man outside of his element, often in awe of the likes of Wonder Woman and Superman
. He and Wonder Woman developed a connection, possibly romantic, during his time working by her side.
His cover remained solid until Wonder Woman recovered from the blindness she suffered from her battle with Medusa
. She had been given new sight by her patron goddess Athena
that gave her new insights on those around her. When she saw Jonah again, she saw that there was something he had been hiding. Not only that, but he was even afraid of her. An emergency called her away before she could question him about his true motives for working for her, and she told Ferdinand
to see to it that he remained at the embassy until she returned. Jonah, knowing his cover was about to be compromised, took this opportunity to leave. Ferdinand tried to stop him but was surprised and overcome by his sudden skill in hand-to-hand combat. He did nothing to harm Ferdinand and only rendered him unconscious.Maxwell Lord
's death at Wonder Woman's hands happened almost immediately after this, and Jonah received the order that all Checkmate assets were being recalled. This was simple enough for him, since he was already on his way back with his cover blown. However, Wonder Woman managed to track him down and intercept his car as he was speeding down the road. She accused him of lying to her, but he countered by saying she just never asked. He told her it was not Maxwell Lord he worked for. It was Checkmate. He knew her well enough to know that if she killed Lord then Lord must have crossed a line that left her with no choice. Wonder Woman had to let him go, because as he said, she could not prove he had done anything more than speeding and she had enough trouble to deal with since she killed Lord.
Jonah returned to Checkmate and stayed with the organization even after it was dismantled and rebuilt under the United Nations. A year after his confrontation with Wonder Woman, he was serving Sasha Bordeaux
as the Black Queen's Knight. He exhibited a friendly and flirtatious relationship with her, despite her being taken by Mr. Terrific
. It was all simply in good humor. On a operation with Sasha and Fire
, they raided a Kobra
base off the Gulf of Aden. He was shot and killed as he and Sasha burst into a room to secure and the Kobra soldier got a shot off before Sasha could take him out. She turned to see that Jonah was dead.