Set some 30 years after the events of "The Mummy's Hand", it seems that the high priest (George Zucco) who resurrected Kharis the Mummy, survived the events at the end of the last film, as did Kharis, and the High Priest has just picked a successor.
Seems they want revenge on the people who plundered Princess Ananka's tomb (took them long enough didn't it?), so they send the young priest, Memhet Bey, over to America, along with a rather large "box", which we know contains more than just his spare clothes, to seek them out.
Bey takes a job as a cemetery caretaker, and soon afterwards, the now elderly explorers from the previous film, Steve Banning and Babe Hanson (wasn't he called Jenson in the last film?) are killed under very suspicious circumstances and the Sheriff is being flooded with calls about a large "Mummy" like creature stalking across peoples farms at night.
Needless to say, it doesn't take them too long to realise that the new Egyptian guy working at the cemetery is probably behind the crimes and when the Mummy kidnaps young Isobelle (Elyse Knox), who's the bride-to-be of Banning's son John (John Hubbard), it's down to a good old fashioned lynch mob to confront Bey, sort out the Mummy and rescue the girl.
Overall, I'd say this is a fairly entertaining follow up if you like old B&W films. It was good to see Dick Foran and Wallace Ford reprising their roles, even though the "Abbot and Costello" style humour between them was absent in this one. It was just a pity they got killed off in this. I also noted that the Mummy was played this time by "Wolf Man" star Lon Chaney Jr, as opposed to Tom Tyler who'd played Kharis in the original.
But anyway, if you liked the first film, you should enjoy this.