Bell was Head of the Decorative Arts Department at Liverpool School of Architecture and Applied Arts (1894-99). From the turn of the 20th century he focused on religious, mythological and allegorical subjects. As the title indicates, the three figures in the foreground are being warned of an attack. Their companion is waving at them frantically in the distance. The intended period of this watercolour’s subject is unclear. The style of dress suggests that it is an imaginary event from the history of the ancient Britons. It could illustrate the Roman invasion of the British Isles or perhaps a theme from Greek mythology.