Matthew Carroll (plaintiff) brought suit against Stryker Corporation (defendant) for unpaid wages and other compensation under Wisconsin’s wage-claim statute and, alternatively, sought recovery under the equitable-contract doctrines of quantum meruit and unjust enrichment. Stryker moved the case to federal court, where it filed a motion for summary judgment, arguing that Carroll did not fall within the scope of Wisconsin’s wage-claim statute because he worked on commission and that Carroll was not entitled to equitable relief because the parties had entered into an express contract. Carroll voluntarily dismissed his statutory claim. The district court granted Stryker’s motion for summary judgment as to Carroll’s equitable claims. Carroll appealed.