The article explores how mergers can affect prices and welfare in industries with secret contracts between producers and sellers. They studied scenarios where two suppliers sell to two retailers and found that prices remain unchanged regardless of who holds the power in negotiations. Comparing two types of mergers, they discovered that a downstream merger, giving power to the retailer, harms welfare more than an upstream merger favoring the supplier. Interestingly, observable contracts make no difference in the impacts of downstream and upstream mergers. In a nutshell, when it comes to secret agreements in the supply chain, which side merges matters for consumers and the market.