His Lordship's Return - His Lordship's Mysteries, #3

For Dominick and Alfie, it feels like they've only just settled into life at Balcarres House when an urgent letter from an old friend has them racing back to London. However, they're not returning to Alfie's swirling ton of money and nobility, but to the dark underside of the city that Dominick knows all too well. In a desperate race against time, they'll have to walk streets that Alfie barely remembers and Dominick hoped to forget.
Their return brings up terrors better left in the past and for one of them, the strain may be too much to bear. Under the shadow of the workhouse, they'll have to act quickly to stop a killer or the lives lost may be their own. His Lordship's Return is the third novel in the His Lordship's Mysteries series.