Young David Sanders is given a very special magnifying glass by a terminally ill neighbour, Mr Silver, who asks him to take on a life long responsibility of using the magic powers of the magnifying glass to help police solve complex crimes. The magnifying glass, which is called Focal, enables David to look back in time to see images of the the past but only for a limited period. David and his parents, Paul and Laura, agree to help David and to keep Focal's secret.

David slowly comes to understand both the power and limitations of Focal and uses it to secretly uncover details of crimes which are baffling the police. In doing so, he takes on disguises to protect his identity and the secret of Focal Justice, the name which the media have given to the person who provides incredibly detailed crime information to the police.

Books are best read in sequence.

Book Four. David's local community is shocked when a blackmailer threatens a local supermarket chain with poison in their products. David uses the power of Focal to work out how he is delivering the poison and tracks him back to his location enabling the police to catch him.