‘Slow Horses’ settles into a familiar, but welcome, groove

Slow Horses was something of a slow-burning surprise when its first season launched back in April. It was yet another Apple TV hit whose marketing hadn’t done well enough to connect with audiences, relying instead on word of mouth. What viewers found, however, was a low-stakes spy drama with the sort of pulpy, throwback thrills that you rarely see in our more self-serious age. Mixed with a shot or two of black comedy, and it made for a surprisingly gripping package I felt compelled to rave about back in April.