The rag-tag group of street kids known as the Irregulars first appeared in the Sherlock Holmes novel A Study in Scarlet in 1887. This time, the Irregulars find themselves having to solve the mysterious disappearance of two of their own gang, while Holmes himself is accused of murder and put under house arrest. Only by the combination of all their skills can they hope to free Holmes and the kidnap victims, solve the murders and prevent an audacious heist.