CSI: Miami - 4.1

It hardly seems fair to refer to CSI: Miami as a spin-off these days, since it has taken a path that is uniquely its own. Initially tied to a similar formula to that of its older Vegas-based sibling, it was all about getting from A plot to B plot with little in between.

By the first part of its fourth season, however, the characters - most notably Horatio Caine (David Caruso) - have been allowed to flourish into fully rounded personalities, complete with foibles, quirks and - CSI Las Vegas take note - credible and exciting back stories. Even more importantly, the writers have created several story arcs which run across the season making it a much more unmissable watch than its desert-based cousin - although these arcs make the fact that the season is released in two lumps, months apart, all the more annoying.

All the characters have something going on this season, with emotions high on the agenda. Horatio, always assumed to be a saint is haunted by a 'sin' from his past and the ghost of case that won't stay dead. This just happens to provide the perfect opportunity for a crossover episode with CSI: NY (though the NY half of the story is sadly not contained on this collection). Calleigh Duquesne (Emily Procter, going from strength to strength as the series progress), meanwhile, has serious men trouble and things are getting dicey on the homefront for Eric Delko (Adam Rodriguez), whose love for his sister may put his job on the line. Things aren't any quieter for Ryan Wolfe (Jonathan Togo) who faces accusations of ratting out his colleagues to his squeeze on a news channel and also has a nasty brush with a nail gun. Even morgue momma Alexx Woods (Khandi Alexander) makes it out of the mortuary to confront a criminal. All this, plus the usual solid supporting performance from Rex Lin as faithful old copper Tripp and new lab rat on the block Natalia Boa Vista (Eva LaRue Callahan), who fuels a feud between Wolfe and Delko.

By ripping up the formula sheet and investing in the characters, Miami is as gripping as any cop show on the box. Caruso has developed his character so fully that his quirks are almost an artform - from the donning of his trademark specs to the earnest promises he makes to children, while down on his haunches. This season he shows, more than ever, a frailty beneath his character's fierceness that makes compelling viewing.

The direction is slick and the cinematography inspired - although scenes where there is a heavy reliance on CGI betray their limited budget - most notably fire scenes on a boat in Blood On The Water, where less computer trickery would have probably made for a more believable look. Also, the latest lab set is on the ridiculous end of gloss. Featuring more glass than you average greenhouse, it looks more like something from Star Trek than a genuine police HQ.

These are merely niggles in the face of greatness, however. By employing more flexibility in terms of storylines, the Miami characters feel more real, although each episode still offers a genuinely satisfying mystery. In fact, the first part of series four is so strong in terms of both story and cast, that it is hard to pick a standout episode.

Those who like an adrenaline rush will certainly get a kick out of the explosive opening sequence of From The Grave and enjoy the blistering pace of Nailed, which features an injured CSI. Others keen on twisting plots will probably count Three Way - in which a trio of holidaying wives all seem to have committed the same crime of passion - or Blood On The Water - a deadly puzzle on a boat - as one of their favourites. Those after character and story arcs, however, will doubtless cite Under Suspicion - which sees Caine come under scrutiny for a murder - as top of the tree. Like global warming, Miami just gets hotter.